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First Mining Discovers New High-Grade Gold Occurrences at its Birch-Uchi Greenstone Belt Project

Drill Results

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NEWS RELEASE

First Mining Discovers New High-Grade Gold Occurrences

at its Birch-Uchi Greenstone Belt Project

December 5, 2023 – Vancouver, Canada – First Mining Gold Corp. (“First Mining” or the “Company”)

(TSX: FF) (OTCQX: FFMGF) (FRANKFURT: FMG) is pleased to announce the discovery of new gold

occurrences confirmed from rock sampling assay results from its 2023 exploration program at its Birch-

Uchi Greenstone Belt Project (“BUGB Project” or the “Project”) located near its flagship Springpole Gold

Project (“Springpole”) in northwestern Ontario, Canada.

Exploration assay results have identified a new near- surface and high priority structural setting for gold

mineralization approximately 375 metres from the recently drill tested Saddle target which returned 0.92

g/t Au over 114 m (see news release dated July 6, 2023). Rock samples assay ed at the now-established

Challenger target are encouraging, as highlighted by the discovery of two new mineralized occurrences

approximately 60 m apart, where grab samples have returned gold values including 25.60 g/t Au, 7.10 g/t

Au and 4.42 g/t Au (Figure 1). Further gold assays associated with the Challenger target now define an

interpreted east-west trending gold mineralized shear structure over an approximately 60 m trend, which

remains open both along strike and at depth. The Challenger target and recently tested Saddle target are

located approximately 12 km southwest of Springpole.

"This discovery of a new zone of outcropping gold mineralization is a significant advancement in our

regional exploration efforts for the Birch -Uchi Greenstone Belt project,” stated Dan Wilton, CEO of First

Mining. “Our ability to identify higher- grade gold mineralization only 375 metres from our successful

drilling of the Saddle target demonstrates the strong potential for a significant gold endowment

regionally. Challenger represents a strong opportunity to further grow the Saddle area exploration

opportunity through additional field campaigns, strongly validating our exploration strategy and targeting

methodology.”

Challenger Target Highlights:

• Two newly discovered gold mineralization occurrences within 60 m of each other, with samples

grading up to 25.60 g/t Au

• Close proximity to an expanding gold mineralization system (375 m NW of Saddle) identified in

First Mining’s 2023 winter drill program, where Saddle drilling returned 0.92 g/t Au over 114 m

• Employed geoscience systems approach to characterize the target geology, supporting additional

exploration opportunities in close proximity to the Challenger and Saddle target areas

• BUGB Project is proving to be prospective with increa singly advanced and catalogued targets

providing for future resource potential

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Figure 1: Challenger Discovery and Saddle Target Location, 12 km SW of the Springpole Deposit

Table 1: Selected Rock Grab Sample Assays from the Challenger Target

Sample ID UTM (E) UTM (N) Au (g/t) Target

C261398 538281 5688632 25.60 Challenger

C261809 538231 5688633 7.10 Challenger

C261397 538283 5688630 4.42 Challenger

Note: Rock grab samples are selective in nature and may not be indicative of the true grade and style of

mineralization on the property

Challenger Target

The Challenger target is located approximately 12 km southwest of First Mining’s Springpole Gold Project

(see Figure 1), which hosts a NI 43-101 mineral resource totalling 4.6 million ounces of gold at 0.94 g/t Au

in the Indicated category and 0.3 million ounces of gold at 0.54 g/t Au in the Inferred category*. The

Challenger target is hosted within the BUGB project area, where locally a significantly deformed and

mineralized granodiorite intrusive occurs in contact with clastic sedimentary turbidites and

conglomerates. Mineralization is associated within an increased silica and carbonate altered and sheared

structure over an exposed strike length of 6 0 metres , with high concentrations of multiphase quartz

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veining within a thick bedded turbidite sequence. The dominant sulphide mineralization is composed of

pyrite and occurs as very fine-grained disseminations averaging an abundance of 1 -5%. At least two

generations of quartz veining are documented subparallel and orthogonal to the controlling structure and

vary from 1 cm to 50 cm in scale . Mineralization appears to occur within geophysical resistivity low

signatures interpreted to be large -scale folding within the clastic sedimentary lithology (Figure 2). The

2023 field results indicate that a high-grade mineralized structure exist s along meaningful strike length

and therefore warrants follow-up exploration.

Figure 2: Photo of Newly Discovered Challenger Area Alteration and Shear Gold Occurrence

* Details of the Springpole Gold Project mineral resource can be found in the technical report entitled “NI 43 -101

Technical Report and Pre-Feasibility Study on the Springpole Gold Project, Ontario, Canada” which was prepared by

AGP Mining Consultants Inc. in accordance with National Instrument 43 -101 Standards of Disclosure for Mineral

Projects (“NI 43-101”) and has an effective date of January 20, 2021.

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Regional Exploration

The Saddle and Challenger target areas represent underexplored opportunities that have been subject to

limited historical prospecting and geoscience programs of induced polarization (IP) and airborne magnetic

geophysics, as well as diamond drilling completed in the 1980s . S ince that time, further field-based

exploration activities at these prospective areas have been limited. First Mining believes that a modern

exploration approach inclusive of additional diamond drill testing is warranted.

In 2021, First Mining completed a focused field campaign that targeted regional gold occurrences

including grab samples at Rice (7.54 g/t and 2.67 g/t), Green (1.79 g/t), and Exit and Trench Grid (4.8 g/t),

that form a notable trend with the Saddle and Challenger target areas over a projected 1 km strike length.

Opportunities for expanding the mineralization system and the potential for exploring within a related

structural setting have elevated the regional prospectivity in advancing the area.

Exploration completed in First Mining’s 2022 field campaigns further advanced geologic understanding of

the area, with data collection supporting an integrated 3D exploration model. Surface grab sample results

from the 2022 campaign returned assay results which vector towards a mineralization setting that

includes several structures surrounding and proximal to an intrusi ve cent re, with h igher-grade grab

samples found proximal to the contact of the sedimentary host rock and the felsic intrusive unit.

In 2022 , the Company conducted additional a irborne geophysical surveying that supported improved

targeting resolution for exploration drilling . Through processing and interpretation , modelled shear

zone(s) coincident with mineralization have been interpreted which has proved to be valuable in step-out

exploration planning.

During the 2023 winter program, First Mining successfully completed 842 m of drilling in 5 exploration

drill holes focused on the Saddle target (see news release dated July 6, 2023 ). Drilling was aimed at

validating the newly developed 3D exploration model, underpinned by historical drilling and field -based

data collection, as well as testing extensions along strike, at depth, and across an interpreted fault offset.

The results from the 2023 winter drilling highlight robust intervals of consistent gold mineralization over

significant widths including 0.92 g/t Au over 114 m and 0.75 g/t Au over 57.70 m (drill hole SAT23-001).

The program has been successful in confirming the continuation of the mineralization envelope along the

shear structure, opening up the exploration growth potential around the Saddle target which continues

to demonstrate an evolving gold mineralization setting with advancing exploration.

2023 Summer Field Campaign

The 2023 summer field campaign for the Saddle area followed up on key geological features with a specific

focus on geochemistry and geophysical signatures which have been interpreted to be related to Saddle

gold mineralization. First Mining’s exploration teams this year completed regional infill mapping transects

and conducted prospecting in previously underexplored areas.

Through mapping and prospecting, 56 grab samples were taken across the area, of which 18 grab samples

were taken in the Challenger target area, 46 outcrop stations were mapped, and 51 regional soil samples

were collected.

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Results of the Saddle target follow -up exploration program confirmed surface mineralization, shear

structures and an alteration expression that is coincident with a series of resistivity low signatures.

Regional transects were then conducted to the north of the Saddle target to further infill outcrop mapping

as well as prospect a sub-parallel resistivity low trend which occurred proximal to an area of anomalous

gold in historical soil samples (100 ppb Au). Investigation of the geoscience components led to the new

discovery.

Initial assay results for samples from the Challenger target discovery returned 25.6 g/t Au and 4.42 g/t Au

in rock grab assays along a regional transect , prompting further in-field mapping and sampling to better

characterize and validate the relationship between mineralization, alteratio n and the resistivity low

extending along trend. Assay results from the follow-up campaign further validated this signature at the

Challenger target and established a 60 m strike extension between a 25.6 g/t Au and 7.1 g/t Au rock grab

sample (Figure 2). On a regional scale, the Challenger as well as the Rice and Saddle targets are supportive

of two favourable resistivity low expressions that average up to ~100 m in width, have a ~600 m estimated

strike length and form a positive vector for follow-up exploration programs (Figure 3).

All assay results from the Challenger target grab sample program are reported below in Table 2 which

includes sample location data.

“The Challenger target is an important new discovery for our exploration teams that is illustrative of the

rewarding opportunities in a sustained and fundamental geoscience approach. We continue to

demonstrate a growing exploration story in the renowned Red Lake Mining District that is proven to host

large-scale, high value gold deposits,” stated James Maxwell, VP Exploration at First Mining.

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Figure 3: Geological Compilation Map of the Challenger Target and its S patial Relationship to the Saddle and Rice

Targets. Grab assay results are highlighted within IP Resistivity low.

Table 2: Assay Results at the Challenger Target

Sample ID UTM (E) UTM (W) Grade ( Au g/t) Target

C261397 538283 5688630 4.42 Challenger

C261398 538281 5688632 25.6 Challenger

C261801 538278 5688629 2.81 Challenger

C261802 538281 5688624 3.10 Challenger

C261803 538283 5688623 2.90 Challenger

C261804 538285 5688626 0.71 Challenger

C261806 538283 5688625 0.19 Challenger

C261807 538279 5688623 0.09 Challenger

C261808 538281 5688624 0.04 Challenger

C261809 538231 5688633 7.10 Challenger

C261810 538233 5688639 0.38 Challenger

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Sample ID UTM (E) UTM (W) Grade ( Au g/t) Target

C261811 538230 5688634 0.06 Challenger

C261812 538232 5688636 0.39 Challenger

C261813 538223 5688635 0.01 Challenger

C261814 538226 5688634 0.07 Challenger

C261816 538226 5688634 0.11 Challenger

C261817 538238 5688628 3.76 Challenger

C261818 538223 5688641 0.01 Challenger

About the Birch-Uchi Greenstone Belt

First Mining’s BUGB Project hosts significant district -scale exploration leverage in forming part of a

consolidated >70,000 hectare mineral tenure . The property and broader greenstone belt hosts historic

production centres that are demonstrative of the strong gold endowment and an affinity for potential

new discovery. First Mining’s extensive BUGB property position is located within the Red Lake Mining

District and is situated approximately 80 km east of the Red Lake Mines Complex of Evolution Mining, and

75 km northeast of Kinross Gold’s Dixie Project (formerly owned by Great Bear Resources Ltd). Geology

of the region is comprised of Archean Greenstone terranes that are endowed by significant go ld

mineralization inclusive of orogenic and alkaline intrusion-related deposit styles. Initial data compilation

and validation to date has indicated that the region demonstrates an underexplored and previously

fragmented exploration immaturity that is well levered to the Company’s strategy of consolidation and

district screening.

The BUGB hosts multiple gold mineralization styles throughout, which supports having a strong multi -

discipline geoscience foundation that can be applied in an integrated and iterative targeting approach .

Early targeting and vectoring elements highlight consolidated target opportunities surrounding the

Springpole Project.

Analytical Laboratory and QA/QC Procedures

All sampling completed by First Mining within its exploration programs is subject to a Company standard

of internal quality control and quality assurance (QA/QC) programs which include the insertion of certified

reference materials, blank materials and a level of duplicate analysis. Grab samples from the 2023 field

program were sent to AGAT Laboratories in Thunder Bay, Ontario, and Calgary, Alberta, where they were

processed for gold analysis by 50 gram fire assay with an atomic absorption finish, and multi -element

analysis (including silver) by inductively coupled plasma (ICP) method with a four acid digest. AGAT

Laboratories systems conform to requirements of ISO/IEC Standard 17025 guidelines and meets assay

requirements outlined for NI 43-101.

Qualified Person

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Hazel Mullin, P.Geo., Director, Data Management and Technical Services of First Mining, is a “Qualified

Person” for the purposes of NI 43-101 Standards of Disclosure for Mineral Projects, and she has reviewed

and approved the scientific and technical disclosure contained in this news release.

About First Mining Gold Corp.

First Mining is a gold developer advancing two of the largest gold projects in Canada, the Springpole Gold

Project in northwestern Ontario, where we have commenced a Feasibility Study and permitting activities

are on-going with a draft Environmental Impact Statement (“EIS”) for the project published in June 2022,

and the Duparquet Project in Quebec, a PEA stage development project located on the Destor-Porcupine

Fault Zone in the prolific Abitibi region. First Mining also owns the Cameron Gold Project in Ontario and

a portfolio of gold project interests including the Pickle Crow Gold Project (being advanced in partnership

with Auteco Minerals Ltd.), the Hope Brook Gold Project (being advanced in partnership with Big Ridge

Gold Corp.), and a large equity interest in Treasury Metals Inc.

First Mining was established in 2015 by Mr. Keith Neumeyer, founding President and CEO of First Majestic

Silver Corp.

ON BEHALF OF FIRST MINING GOLD CORP.

Daniel W. Wilton

Chief Executive Officer and Director

For further information, please contact:

Toll Free: 1 844 306 8827 | Email: [email protected]

Paul Morris | Director, Investor Relations | Email: [email protected]

Richard Huang | Vice President, Corporate Development | Email: [email protected]

Cautionary Note Regarding Forward-Looking Statements

This news release includes certain “ forward-looking information” and “ forward-looking statements” (collectively

“forward-looking statements”) within the meaning of applicable Canadian and United States securities legislation

including the United States Private Securities Litigation Reform Act of 1995. These forward- looking statements are

made as of the date of this news release. Forward -looking statements are frequently, but not always, identified by

words such as “ expects”, “anticipates”, “believes”, “plans”, “projects”, “ intends”, “estimates”, “envisages”,

“potential”, “possible”, “strategy”, “goals”, “opportunities”, “objectives”, or variations thereof or stating that certain

actions, events or results “may”, “could”, “would”, “might” or “will” be taken, occur or be achieved, or the negative

of any of these terms and similar expressions.

Forward-looking statements in this news release relate to future events or future performance and reflect current

estimates, predictions, expectations or beliefs regarding future events. All forward-looking statements are based on

First Mining's or its consultants' current beliefs as well as various assumptions made by them and information

currently available to them. There can be no assurance that such statements will prove to be accurate, and actual

results and future events could differ materially from those anticipated in such statements. Forward- looking

statements reflect the beliefs, opinions and projections on the date the statements are made and are based upon a

number of assumptions and estimates that, while considered reasonable by the respective parties, are inherently

subject to significant business, economic, competitive, political and social uncertainties and contingencies. Such

factors include, without limitation the Company’s business, operations and financial condition potentially being

materially adversely affected by the outbreak of epidemics, pandemics or other health crises, such as COVID-19, and