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Iamgold Announces Côté GOLD Project Progress Update and Positive Results of the 2023 Gosselin Drilling Program

Exploration Programs

NEWS RELEASE TSX: IMG NYSE: IAG

IAMGOLD ANNOUNCES CÔTÉ GOLD PROJECT PROGRESS UPDATE AND POSITIVE

RESULTS OF THE 2023 GOSSELIN DRILLING PROGRAM

All monetary amounts are expressed in U.S. dollars, unless otherwise indicated.

Toronto, Ontario, October 23, 2023 – IAMGOLD Corporation (NYSE:IAG, TSX:IMG) (“IAMGOLD” or the “Company”) is

pleased to announce an update for the Côté Gold project highlighting the construction progress in the third quarter,

alongside additional assay results from its continuing diamond drilling program at the Gosselin zone discovery located

immediately adjacent to the Côté Gold deposit. The advancement of Côté Gold and the Gosselin delineation drilling program

is being undertaken as part of the Côté Gold joint venture between IAMGOLD, as the operator, and Sumitomo Metal Mining

Co., Ltd. ("SMM"). Côté Gold is located in Ontario, Canada and is currently under construction with production expected to

commence in early 2024.

Highlights of Q3 2023 Côté Gold Construction Progress

• As of September 30, 2023, overall project progress for Côté Gold was estimated to be 90.6% complete , with

construction progress approximately 92% complete.

• Strong performance on health and safety during peak construction with over 1,800 workers at site – bringing total

project hours worked to 13.2 million hours with a project-to-date TRIFR of 0.68.

• Earthworks on the TMF has allowed the dams to achieve elevation milestones to enable the filling of the TMF with

water to store the 1.1 – 1.5 million cubic metres required for commissioning and initial operation.

• Demobilizing contractor with IAMGOLD operating teams successfully taking control of pit, dewatering , pioneer

drilling and overburden stockpile activities from the contractor.

• Significant progress in the dry and wet areas of the process facility, as bulk construction activities are winding down,

ushering in the finishing and completion stages.

• Electrification of the site is ongoing following connection to the provincial hydro grid.

• Commissioning and Pre-commissioning teams are working with construction teams to coordinate the overlapping

of pre-operation activities with remaining construction.

• Autonomous mining haul trucks have continued to ramp up, with ten CAT 793F currently operating autonomously

and a total of fourteen commissioned.

• Mining activities have built the current ore stockpile to 3.7 million tonnes of material, on track to the target build -up

of 5.0 million tonnes by the end of the year.

• Hiring of key positions for operations has progressed well with 400 roles filled to date.

Highlights of the Gosselin drilling program

• 472.0 metres (“m”) at 0.65 grams per tonne gold (“g/t Au”) in drill hole GOS23-131 from 152.0 m including:

o 51.0 m at 1.59 g/t Au from 389.0 m;

• 356.0 m at 0.82 g/t Au in drill hole GOS23-133 from 275.0 m including:

o 132.0 m at 1.09 g/t Au from 440.0 m;

• 300.8 m at 1.40 g/t Au in drill hole GOS23-134 from 554.5 m including:

o 207.3 m at 1.71 g/t Au from 648.0 m;

• 240.0 m at 1.53 g/t Au in drill hole GOS23-136 from 318.0 m including:

o 120.0 m at 2.26 g/t Au from 421.0 m;

• 500.8 m at 0.72 g/t Au in drill hole GOS23-144 from 182.0 m.

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Renaud Adams, President and Chief Executive Officer of IAMGOLD, stated: “It is an exciting time for IAMGOLD as we near

the finish line of construction at Côté and start a new chapter at IAMGOLD. This is a project that is critical for the repositioning

of this company, as when Côté Gold comes online, the Company will have a significantly higher production base and lower

cost profile, providing a strong foundation of cashflow and growth opportunities in Canada . We have seen remarkable

progress and transformation of the project and we are excited to host our investor and analyst tour at site tomorrow to allow

for the group to not only see the advancement of the asset but to have the opportunity to see the confidence of the team on

the ground as we approach commissioning and the ramp up of production next year.”

Commenting on the Gosselin drilling program, Craig MacDougall, Executive Vice President, Growth for IAMGOLD, stated:

"This d iamond drilling program has strategically targeted the expansion potential of the Gosselin deposit at depth,

specifically below the East and newly discovered West hydrothermal breccia bodies, the gap area between these breccia’s,

and also along the southern edge of the deposit . The assay results confirmed the extension of gold bearing altered and

mineralized hydrothermal breccia and associated tonalite intersected in numerous drill holes up to 400 metres vertically

below the previous resource pit shell over an approximate one-kilometer strike length. The results are very encouraging

and indicate that the Gosselin deposit, subject to the completion of further delineation drilling, has potential to expand in

size similar to the adjacent Côté deposit.”

Côté Gold Project Progress in Q3 2023

As of September 30, 2023, on an overall project progress basis, Côté Gold was estimated to be 90.6% complete, with

construction progress approximately 92% complete. The following provides an update on project activities:

Project Activity Update

Health and safety Total project hours worked of 13.2 million hours with a project-to-date DARTFR of 0.06 and

a TRIFR of 0.68.

Labour and workforce In September, the project workforce averaged between 1,800 and 1,900 workers on site.

Activities at site have started the shift from major construction to finalization and

commissioning. Labour availability and turnover continues to be a primary focus for Côté

management.

Earthworks activities The TMF east starter dam reached the Phase 1 elevation of 396, and the West starter dam

is substantially complete at its final elevation of 410.5 EL. These milestones enable filling

the TMF with water to store the 1.1M -1.5M m3 required for commissioning. At the end of

September, 0.8M m3 of water has been accumulated in the TMF.

Bulk fill for the Phase II TMF has reached target elevation; sand bedding and liner work is

being completed in the fourth quarter.

The primary earthworks contractor demobilized during the quarter, successfully handing off

pit, dewatering, pioneer drilling and overburden stockpile activities to IAMGOLD operations

teams.

Processing plant Progress for both the dry and wet areas of the process facility advanced well in the quarter.

It is anticipated bulk construction will end in October, ushering in the finishing and

completion stages.

The HPGR and secondary crushing building progressed well in the quarter, with the

installation of most of the secondary crusher components. All conveyors have been erected

for the HPGR and secondary crusher building marking a major milestone.

In the coarse ore area, the triodetic dome cladding was substantially complete at quarter

end. Conveyors and interconnecting electrical has been turned over to the Pre -

commissioning team. The screen building saw the installation of the screens, conveyors

and belts. The fine ore bin area is substantially complete, with walkdowns completed for

most subsystems.

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Installation of ball mill liners is complete, and motors and motor soleplates were set. The

alignment on the ring gear for the ball mill was found to be out of tolerance. The OEM

service team is on site to address the problem.

Leach and CIP tank installation continues to be a primary focus with final completion

expected early in the fourth quarter. Leak testing of leach tanks and thickeners commenced

in October. Construction sequence has been adjusted to prioritize critical tanks for

commissioning to mitigate potential delays on the overall schedule.

Infrastructure Commissioning of the main electrical substation and the connection to the provincial hydro

grid and the substation was completed in the quarter. The substation was energized

successfully and connections throughout the site are ongoing.

Installation of underground services and utilities continued to progress. Fuel distribution

and storage, including the refueling station, has been commissioned and completed.

Truck shop building A was completed in the quarter, followed by building B in the fourth

quarter. All cranes are commissioned with OH doors installed, and fire proofing started in

building B. The installation of the electrical room for the assay lab is ongoing with handover

to operations planned in October.

Procurement Heavy mobile equipment continues to arrive on site with fourteen CAT 793F haul trucks,

two 6060 electrical shovels, three 994 loaders and three D10 dozers having been delivered

by the end of September.

Commissioning of the first electric shovel is ongoing, awaiting completion of electrification

in order to be deployed for in-pit activities.

Operational readiness Commissioning and Pre -commissioning teams are working with construction teams to

coordinate the overlapping of pre -operation activities with construction. Operational

readiness continues in multiple areas with a focus on ramping up mining activities, hiring

and training of process plant personnel, development and standardization of mine, mill and

site maintenance processes and systems, and preparation for the transition of site services

contracts.

Autonomous hauling continued to ramp up. During the third quart er 2023, up to ten CAT

793F haul trucks have begun operating in autonomous mode and a total of fourteen haul

trucks have been commissioned. Autonomous drilling began in the quarter with four Pit

Vipers now in operation. The operations team are continuously improving haulage roads

and dumping location to achieve improved autonomous haulage efficiency and cycle times.

Mining activities advanced, progressing down to the 364 m EL bench grade in the south

area, and starting of mining to the same level in the east. Owner mining has progressed

well with nearly 1.6 million tonnes mined in the third quarter 2023. The ore stockpile has

approximately 3.7 million tonnes of material on track to the target build -up of 5.0 million

tonnes by the end of the year. The IAMGOLD mine operations team started operating 24/7

effectively in July and is at full complement as of quarter end.

The 2022/2023 48,000 m RC drill program de -risking the first year of the mine plan was

completed. A new 30,000 m contract has been awarded with drilling commenced at the end

of the quarter.

Permitting and sustainability All critical permitting and sustainability work is complete with non-critical path work ongoing

and expected to be received during the remainder of the project.

Community consultation and the implementation of the IBA with Indigenous partners

continue. The health, safety and environmental programs and the emergency response

plan are in development along with standard operating procedures.

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Upcoming Milestones and Schedule Summary

Côté Gold is expected to commence production in the first quarter of 2024. Construction of the project commenced in the

third quarter 2020 and major earthworks commenced in the first quarter 2021. Recently achieved milestones and those

remaining of note are as follows:

Côté Gold Upcoming Milestones

The Company notes that potential further impacts, including, without limitation, inflationary pressures, global supply chain

disturbances, disruptions from weather events resulting in limited or no productivity such as extreme cold or forest fires in

dry, hot summer months, labour disputes and the tight labour market could impact the timing of activities, costs, availability

of workforce, productivity and supply chain and logistics and, consequently, could further impact the tim ing of actual

commercial production and, consequently, project costs.

To view an interactive 3D model of the Côté Project progress and deposits please use the following link or visit our website:

https://vrify.com/decks/14351 (updated to August 31, 2023, excluding Gosselin results below).

Gosselin Drilling Program Results

IAMGOLD is reporting assay results from an additional twenty-one (21) diamond drill holes totaling 16,495 metres completed

between January 20 and August 24, 2023. The assay results reported are provided in Table 1 below (refer to plan map for

drill hole locations outlined in Figures 1 and 2).

The favorable results from this phase of drilling provide evidence the Gosselin deposit is approaching similar dimensions

as the adjacent Côté deposit. Drill intercepts obtained from the newly discovered West Breccia have significantly expanded

this breccia body which now measures 250 metres by 170 metres and extends for a depth of approximately 400 metres.

This has helped to highlight a highly prospective corridor at depth measuring up to 850 metres in strike length that remains

to be tested between the Gosselin West Breccia and the Côté Deposit hydrothermal breccia. This represents a priority

exploration opportunity to further expand the Gosselin resource below the 400 meter vertical depth extent of the current

2021 resources pit shell.

Continuing technical studies on Gosselin have advanced in 2023 in conjunction with the diamond drilling program. A drill

core sampling program was completed and submitted for additional metallurgical test work to evaluate comminution

characteristics and gold recoveries over a range of ore types and grades. Also mining and infrastructure studies continue

to review alternatives to optimize the possible inclusion of the Gosselin deposit into a future Côté Gold life-of-mine plan.

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Figure 1 – Gosselin drill hole surface plan and 2023 assay highlights

Figure 2 – Gosselin Composite Longitudinal Section (Figure still in edition)

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Next Steps

The 2023 diamond drilling program continued to successfully demonstrate extensions of the Gosselin Deposit both at

depth (below 400 metres vertical depth) and along the south edge of the deposit. These results will be incorporated into

the deposit model to support an updated Mineral Resource estimate as part of the year end Mineral Resources

disclosure.

Planning is currently underway for the next phases of diamond drilling, with the goal to complete expansion drilling of the

Gosselin Resource to the same depth as the Côté Resource pit (approximately 825 metres vertical) and to complete

additional in-fill drilling to improve resource classification. Technical studies will continue to advance metallurgical testing,

along with planned mining and infrastructure studies.

About the Gosselin Deposit

The Gosselin deposit is located immediately adjacent to the northeast of the Côté Gold deposit and is accessible by

construction roads on the mine property. Diamond drilling to date has delineated wide intervals of low-grade gold

mineralization hosted in altered and brecciated intrusive lithologies similar to that observed at the adjacent Côté Gold

deposit, extending from the Young-Shannon historical shaft in the west to the Gosselin zone in the east. Drilling to date

has outlined mineralization over a strike length of 1,400 metres, width of 400 metres and a depth extent of up to 800

metres. The deposit outcrops below the shallow Three Ducks Lake, and remains open at depth, to the northwest, and

along strike to the northeast and southwest.

Current estimated Mineral Resources at the Gosselin deposit are comprised of 124.5 million tonnes of Indicated

resources grading 0.84 grams of gold per tonne for 3.35 million ounces of contained gold and 72.9 million tonnes of

Inferred resources grading 0.73 grams of gold per tonne for 1.71 million ounces of contained gold at overall grade similar

to the Côté Gold deposit (refer to Company news release dated October 18, 2021).

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Table 1: Gosselin Project Drilling Results - 2023 Drilling program

Hole No. UTM NAD83 Zone17 AZ DIP EOH From To Core Interval

(1) Au (2) (3)

Easting Northing Elev. (°) (°) (m) (m) (m) (m) (g/t)

GOS23-130 430897 5267364 386 359 -57 858.00 6.20 26.00 19.80 0.43

170.00 199.50 29.50 0.83

283.00 353.00 70.00 0.96

359.00 430.20 71.20 0.39

GOS23-131 431186 5267520 382 333 -62 795.00 152.00 624.00 472.00 0.65

Including (3) 389.00 440.00 51.00 1.59

GOS23-132 430896 5267350 387 345 -57 843.00 360.00 529.00 169.00 0.62

551.00 570.00 19.00 0.63

609.00 629.00 20.00 1.19

651.00 834.30 183.30 0.74

GOS23-133 431260 5267452 382 335 -60 858.00 275.03 631.00 355.97 0.82

Including (3) 440.00 572.00 132.00 1.09

653.90 781.00 127.10 0.89

GOS23-134 430932 5267201 386 357 -56 969.00 554.50 855.25 300.75 1.40

Including (3) 648.00 855.25 207.25 1.71

866.00 943.00 77.00 0.99

GOS23-135 430843 5267201 388 340 -57 850.00 399.00 563.12 164.12 0.61

640.00 722.35 82.35 0.55

GOS23-136 431314 5267457 385 337 -57 558.00 318.00 558.00 240.00 1.53

Including (3) 421.00 541.00 120.00 2.26

GOS23-137 431247 5267525 383 276 -69 849.60 361.00 384.00 23.00 0.34

481.00 497.00 16.00 2.45

624.90 655.24 30.34 0.62

694.00 734.00 40.00 0.53

GOS23-138 430813 5267332 393 339 -59 852.00 156.00 182.00 26.00 0.50

293.00 626.00 333.00 0.51

GOS23-139 430732 5267327 400 346 -57 849.00 246.00 303.80 57.80 0.60

313.00 719.00 406.00 0.72

GOS23-140 430690 5267369 399 338 -58 780.00 44.00 385.00 341.00 0.46

573.50 639.00 65.50 0.80

GOS23-141 430850 5267450 383 350 -53 852.00 132.00 595.00 463.00 0.52

GOS23-142 431307 5267490 387 3 -59 855.00 367.95 577.00 209.05 0.65

Including (3) 453.00 572.00 119.00 0.95

GOS23-142A 431307 5267490 387 360 -54 850.00(4) 332.90 585.00 252.10 0.68

Including (3) 513.00 561.50 48.50 1.24

GOS23-143 430850 5267450 383 349 -59 792.00 229.00 342.00 113.00 0.52

350.00 402.00 52.00 0.42

567.06 709.00 141.94 0.44

GOS23-144 430970 5268009 388 168 -62 849.00 182.00 682.80 500.80 0.72

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723.00 849.00 126.00 0.42

GOS23-145 430934 5268190 385 195 -60 801.00 353.00 560.20 207.20 0.67

696.40 762.00 65.60 0.49

GOS23-146 430895 5268171 389 185 -55 36.00 Re-collared hole - GOS23-147

GOS23-147 430901 5268182 388 185 -55 750.00 321.00 496.00 175.00 1.00

Including (3) 379.00 425.02 46.02 2.20

GOS23-148 430946 5268133 388 177 -60 858.00 280.00 431.00 151.00 0.70

602.00 617.50 15.50 0.84

812.80 858.00 45.20 1.28

GOS23-149 431248 5267529 383 295 -70 849.00 252.20 265.52 13.32 0.45

362.00 382.00 20.00 0.66

429.00 636.00 207.00 0.60

659.00 836.00 177.00 0.48

Notes:

1. Actual core widths are estimated to be approximately 60 to 95% of the Core Interval.

2. Drill hole intercepts are calculated with a lower cut of 0.30 g/t Au.

3. Assays are reported uncut but high grade sub-intervals are highlighted.

4. Wedge hole off of GOS23-142 and drilled only 791.7 m.

QUALIFIED PERSON AND TECHNICAL INFORMATION

The drilling results contained in this news release have been prepared in accordance with National Instrument 43 -101 Standards of

Disclosure for Mineral Projects (“NI 43-101”).

Al Smith, P. Geo, District Manager – Exploration for IAMGOLD in the Ontario Côte Gold District is the Qualified Person (“QP”) for the

purposes of NI 43-101 and is responsible for the supervision of the preparation, verification and review of the technical information in this

news release.

The QP responsible for the planning, supervision and execution of the diamond drilling program is Brad McKinley, P. Geo, Senior Geologist

for IAMGOLD in the Ontario Côte Gold District. The technical information has been included herein with the consent and prior review of

the above noted QPs.

The technical and scientific information relating to exploration activities disclosed in this document was prepared under the supervision of

and verified and reviewed by Craig MacDougall, P.Geo., Executive Vice President, Growth, IAMGOLD. Mr. MacDougall is a “qualified

person” (a “QP”) as defined in NI 43-101.

CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING INFORMATION

All information included in this news release, including any information as to the Company’s future financial or operating performance and

other statements that express management’s expectations or estimates of future performance, including statements in respect o f the

prospects and/or development of the Company’s projects, other than statements of historical fact, constitutes forward-looking information

or forward -looking statements within the meaning of applicable securities laws (collectively referred to herein as “forward -looking

statements”) and such forward -looking statements are based on expectations, estimates and projections as of the date of this news

release. Forward-looking statements are generally identifiable by the use of words such as “may”, “will”, “should”, “continue”, “expect”,

“budget”, “aim”, “can”, “focus”, “forecast”, “anticipate”, “estimate”, “believe”, “intend”, “plan”, “schedule”, “guidance”, “outlook”, “potential”,

“seek”, “targets”, “cover”, “strategy”, “during”, “ongoing”, “subject to”, “future”, “objectives”, “opportunities”, “committed”, “prospective”, or

“project” or the negative of these words or other variations on these words or comparable terminology. For example, forward -looking

statements in this news release include, without limitation, those under the headings “Outlook”, “Quarterly Updates”, “Exploration”,

“Liquidity and Capital Resources” and “Market Trends” and include, but are not limited to, statements with respect to: the es timation of

mineral reserves and mineral re sources and the realization of such estimates; operational and financial performance including the

Company’s guidance for and actual results of production, costs and capital and other expenditures such as exploration and inc luding

depreciation expense and effective tax rate; the expected costs and schedule to complete construction of the Côté Gold project; the

updated life-of-mine plan, ramp up assumptions and other project metrics including operating costs in respect to the Côté Gold project;

expected benefits from the operational improvements and de-risking strategies implemented or to be implemented by the Company; mine

development activities; the Company's capital allocation; the composition of the Company’s portfolio of assets including its operating

mines, development and exploration projects; the completion of the sale of the Bambouk assets; permitting timelines and the exp ected