O3 Mining : Corporate Presentation

Cautionary Statement and Technical Information

This presentation (the "Presentation") contains "forward-looking information" and "forward-looking statements" (collectively, "forward-looking statements") within the meaning of the applicable Canadian securities legislation. All statements, other than statements of historical fact, are forward-looking statements and are based on expectations, estimates and projections as at the date of this Presentation. Any statement that involves discussions with respect to predictions, expectations, beliefs, plans, projections, objectives, assumptions, future events or performance (often but not always using phrases such as "expects", or "does not expect", "is expected", "anticipates" or "does not anticipate", "plans", "budget", "scheduled", "forecasts", "estimates", "believes" or "intends" or variations of such words and phrases or stating that certain actions, events or results "may" or "could", "would", "might" or "will" be taken to occur or be achieved) are not statements of historical fact and may be forward-looking statements.

In this Presentation, forward-looking statements relate, among other things: the pre-feasibility study for the Marban Alliance project (the "PFS"); the numerous assumptions underlying the PFS, including the mine plan and economic model; the after-tax internal rate of return and net present value modeling of the Marban Alliance project; the capex, life-of-mine and production modeling of the Marban Alliance project; the potential for brownfield value creation; grade estimates; the speculative geology of inferred mineral resources; gold prices; project scope, including mining methodology and infrastructure; processing methodology; the ability, if any, to achieve the project economics described in this Presentation; the mining and processing strategy; the projected infrastructure; the ability, if any, to construct the required infrastructure; the ability, if any, to obtain the required economic and restoration approvals and permits; the current drill program on the Marban Alliance project and the significance of new drill results; potential mineralization; the ability to realize upon any mineralization in a manner that is economic; the ability to complete any proposed exploration activities and the results of such activities, including the continuity or extension of any mineralization; and any other information herein that is not a historical fact may be "forward-looking information".

This "forward-looking information" involves known and unknown risks, uncertainties and other factors which may cause the actual results, performance or achievements of O3 Mining to be materially different from any future results, performance or achievements expressed or implied by such "forward-looking information". Such factors include, among others, risks relating to the ability of exploration activities (including drill results) to accurately predict mineralization; fluctuations in spot and forward prices of gold, silver, base metals or certain other commodities; fluctuations in currency markets (such as the Canadian dollar to United States dollar exchange rate); change in international, national and local government, legislation, taxation, controls, regulations and political or economic developments; relationships with and claims by local communities and indigenous populations; availability of increasing costs associated with mining inputs and labour; the speculative nature of mineral exploration and development (including the risks of obtaining necessary licenses, permits and approvals from government authorities); access to capital; errors in management's geological modelling; the ability of O3 Mining to complete further exploration activities, including drilling; property interests in the Marban Alliance project; the ability of O3 Mining to obtain required approvals and complete transactions on terms announced; the results of exploration activities; risks relating to mining activities; the global economic climate; metal prices; exchange rates; dilution; environmental risks; and community and non-governmental actions.

Although the "forward-looking information" contained in this Presentation is based upon what management believes, or believed at the time, to be reasonable assumptions, O3 Mining cannot assure shareholders and prospective purchasers of securities of O3 Mining that actual results will be consistent with such "forward-looking information", as there may be other factors that cause results not to be as anticipated, estimated or intended, and neither O3 Mining nor any other person assumes responsibility for the accuracy and completeness of any such "forward-looking information".

O3 Mining does not undertake, and assumes no obligation, to update or revise any such "forward-looking information" contained herein to reflect new events or circumstances, except as may be required by law.

Risks and uncertainties about O3 Mining's business are more fully discussed in the disclosure materials filed with the securities regulatory authorities in Canada, which are available on SEDAR (www.sedar.com) under O3 Mining's issuer profile. Readers are urged to read these materials and should not place undue reliance on any forward‐looking statement and information contained in this Presentation.

TECHNICAL REPORTS

Marban Alliance Technical Report

The scientific and technical information in this Presentation relating to the PFS on Marban Alliance is supported by the technical report entitled "Marban Engineering Project NI 43-101 Technical Report & Prefeasibility study, Val-d'Or, Quebec Canada" and dated October 7, 2022 (with an effective date of August 24, 2022) (the "Marban PFS"), which was prepared for O3 Mining Inc. ("O3 Mining"or the "Company") by Ausenco Engineering Canada Inc., G Mining Services Inc. and WPS Canada Inc. The Marban PFS, which has been prepared in accordance with National Instrument 43-101 - Standards of Disclosure for Mineral Projects ("NI 43-101"), is available on SEDAR (www.sedar.com) under O3 Mining's issuer profile. Please refer to the full text of the Marban PFS for details regarding the key assumptions, parameters and methods associated with the PFS on Marban Alliance.

The Marban Alliance PFS is preliminary in nature and has made numerous assumptions about the Marban Alliance project referenced herein, including in relation to the mine plan and economic models of the project. In addition, the Marban Alliance PFS includes indicated mineral resources which have economic considerations applied to them that would enable them to be categorized as mineral reserves.

Cautionary Statement and Technical Information

TECHNICAL REPORTS (CONTINUED)

Alpha Technical Report

The scientific and technical information in this Presentation relating to the Alpha Property is supported by the technical report entitled "NI 43-101 Technical Report, Alpha Property, Québec , Canada" and dated December 23, 2022 (with an effective date of November 10, 2022) (the "Alpha Report"), which was prepared for O3 Mining by G Mining Services Inc. The Alpha Report, which has been prepared in accordance with NI 43-101, is available on SEDAR (www.sedar.com) under O3 Mining's issuer profile. Please refer to the full text of the Alpha Report for details regarding the key assumptions, parameters and methods associated with the scientific and technical disclosure on the Alpha Property.

MINERAL RESOURCES

This Presentation contains information regarding mineral resources estimated at the projects referenced herein. Mineral resources are not mineral reserves and do not have demonstrated economic viability. The estimate of mineral resources may be materially affected by environmental, permitting, legal, title, socio-political, marketing or other relevant issues. In particular, the quantity and grade of reported inferred mineral resources in the estimates referenced in this Presentation are uncertain in nature and there is insufficient exploration to define these inferred mineral resources as an indicated or measured mineral resource in all cases. It is uncertain in all cases whether further exploration will result in upgrading the inferred mineral resources to an indicated or measured mineral resource category.

QUALIFIED PERSON

The scientific and technical information contained in this Presentation has been reviewed and approved by Mr. Louis Gariépy, P.Geo (OIQ #107538), Vice President Exploration of O3 Mining, who is a "qualified person" within the meaning of NI 43-101.

Unless otherwise noted, this Presentation has been prepared based on information available as of March 25, 2024.

CAUTION REGARDING HISTORIC ESTIMATES

This Presentation includes historical information that has been reviewed by O3 Mining's geological team and qualified person. O3 Mining's review of the historical records and information reasonably substantiate the validity of the information presented in this Presentation; however, O3 Mining cannot directly verify the accuracy of the historical data, including the procedures used for sample collection and analysis. There is insufficient exploration on these prospects to define a mineral resource. It is uncertain if after additional exploration a mineral resource will be delineated. Therefore, O3 Mining encourages investors to exercise appropriate caution when evaluating these results.

NON-IFRS FINANCIAL MEASURES

O3 Mining uses in this Presentation, certain non-IFRS measures including, "all-in sustaining cost" or "AISC" and total cash cost". All-in sustaining cost per gold ounce is defined as production costs less gold sales plus general and administrative, exploration, other expenses and sustaining capital expenditures divided by gold ounces. Cash costs are a non-IFRS measure reported by O3 on an ounces of gold sold basis. Cash costs include mining, processing, refining, general and administration costs and royalties but excludes depreciation, reclamation, income taxes, capital and exploration costs for the life of the mine. The Company believes that such measures provide investors with an alternative view to evaluate the performance of the Company. Non-IFRS measures do not have any standardized meaning prescribed under International Financial Reporting Standards ("IFRS"). Therefore, they may not be comparable to similar measures employed by other companies. The data is intended to provide additional information and should not be considered in isolation or as a substitute for measures of performance prepared in accordance with IFRS.

CAUTIONARY NOTE TO U.S. INVESTORS

O3 Mining is subject to the reporting requirements of the applicable Canadian securities laws, and as a result, reports information regarding mineral properties, mineralization and estimates of mineral reserves and mineral resources in accordance with Canadian reporting requirements, which are governed by NI 43-101. NI 43-101 differs significantly from the disclosure requirements of the United States Securities and Exchange Commission (the "SEC") generally applicable to US companies. As such, the information included in this Presentation concerning mineral properties, mineralization and estimates of mineral reserves and mineral resources is not comparable to similar information made public by U.S. companies subject to the reporting and disclosure requirements of the SEC.

Developing The Next Gold Mine in Québec

Quality Assets

Mission

To be a premier gold exploration and mine development company by delivering superior returns to our shareholders and long-term benefits to our stakeholders.

Vision

To become a best-in-class gold producer.

1/ As of March 25, 2024 | Cash position as of March 13, 2024

Project Development

Greenfield Exploration

Advanced Exploration

Strong ManagementFinancial Strength

C$128.0M

Market Capitalization1

C$17.4M

Investments1

C$15.4M

Cash1

12.4%

Ownership in STLLR Gold

(formerly Moneta Gold)

ESG Commitment

• • Protecting the environment and reducing our impact

• • Bringing long-term benefits to our stakeholders

• • 2024 PDAC Sustainability Award

Strong Financial Position

Shareholder Ownership

Key Financials

Major Shareholders

C$1.46

87.7MC$128.0M

Share Price1

Shares Outstanding1

Market Capitalization1

C$32.8MC$10.0MC$105.2M

Cash and Investments1

Convertible Debt2

Enterprise Value1

Analyst Coverage3

Notes:

1/ As of March 25, 2024 | Cash position as of March 13, 2024

2/ The Investor is entitled, at any time prior to June 2028, to convert, in whole or in part, the outstanding principal amount due under the Debenture from time to time into Common Shares at a price equal to $2.05 per Common Share, subject to customary anti-dilution adjustments. See News Release dated June 19, 2023 and entitled "O3 Mining Announces C$10M Convertible Debenture Placement" for additional details.

3/ O3 Mining disclaims responsibility for the content or guidance published by any analysts.

In the last 20 years - Gold Has Sharply

Performed When Interest Rates Decline

Federal Funds Rate vs Gold Price

1/ Bloomberg

Top Canadian Mining Jurisdiction

1/ Fraser Institute 2022 - Investment attractiveness index.

Robust Pipeline of Projects in the Cadillac Break

Project Development 2.9Moz Au1

• • Located 12km from Canadian Malartic, the largest gold mine in Canada operated by Agnico Eagle Mines.

• • Prefeasibility study completed in October 2022 | 160Koz Au over ~10 years LOM

• • Opportunities to de-risk the project through resource expansion, mine optimization, and potential synergies to secure existing processing infrastructure in Val-d'Or & Malartic.

1.7 Moz1 2019

2023

Organic

Growth (Marbenite-Norbenite)

Greenfield Exploration

• • Located north-west of Marban Alliance | Discovery play

• • VMS Potential: Initial results confirm the discovery of a fertile environment supporting a highly prospective VMS deposit.

Advanced Exploration 1.2Moz Au2

• • Located three kilometres from the Lamaque mine operated by Eldorado

• • Option to acquire nearby 1,400tpd Aurbel mill until 2026

1/ Marban Mineral Resource Estimate (M&I 67.7MT @ 1.09 g/t Au & Inf. 3.1MT @ 2.21 g/t Au) , and Malartic H Resource Estimate (Inf. 10.2MT @ 1.04 g/t Au). 2/ Alpha Mineral Resource Estimate (M&I 7.6MT @ 2.00 g/t Au & Inf. 7.1MT @ 3.30 g/t Au).

Marban Alliance - Overview

2/ See Appendix "A" - Marban Mineral Resource Estimate.

Project Overview

• • Marban Alliance PFS completed in October 2022 with post-tax net present value (NPV5%) of C$463M and unlevered IRR 23.2% with 161Koz gold average annual production LOM1

• • Combined Mineral Resources - OP and UG2

  • › 67,692kt @1.09 g/t Au, 2,374 koz ind.

  • › 3,149 kt @ 2.21 g/t Au, 223 koz inf.

• • Optimization trade-off studies underway and we estimate to commence the Feasibility Study in H1-2024

• • Key infrastructure: railway, hydropower, experienced local labour force and technical services

Pre-Feasibility Study Highlights1 - October 2022

PFS

Base Case

Gold Price	US$/oz	$1,700 $1,850 $2,000
Pre-tax	NPV (5%) IRR Payback	C$775M 30.2% 2.8 yrs	C$996M 36.4% 2.4 yrs	C$1,218M 42.4% 2.1 yrs
Post-tax	NPV (5%) IRR Payback	C$463M 23.2% 3.5 yrs	C$595M 27.9% 2.7 yrs	C$726 M 32.3% 2.4 yrs

161Koz	16,500 tpd
C$1,218M
Avg. Annual	Daily Mill
Gold Production	Throughput
1,552Koz	US$882
C$726 M
LOM Gold	LOM AISC
Production	(US$/oz Au)

Marban Post-tax NPV using a US$2,000/oz Gold Price is

C$726M with 32.3% unlevered post-tax IRR

10