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

Toronto, Ontario--(Newsfile Corp. - December 19, 2025) - IAMGOLD Corporation (NYSE: IAG) (TSX: IMG) ("IAMGOLD" or the "Company") is pleased to announce that the Company has completed the previously announced arrangement (the "Transaction") with Northern Superior Resources Inc. (TSXV: SUP) (OTCQB: NSUPF) (GR: D9M1) ("Northern Superior"), pursuant to which IAMGOLD acquired all of the issued and outstanding common shares of Northern Superior (the "NSUP Shares") by way of a plan of arrangement under Division 5 of Part 9 of the Business Corporations Act (British Columbia).

"With the completion of the acquisition of Northern Superior and its assets, IAMGOLD's Nelligan Mining Complex in the Chibougamau-Chapais region of Quebec is now among the largest pre-production gold projects in Canada," said Renaud Adams, President and Chief Executive Officer of IAMGOLD. "We look forward to accelerating our exploration program in the region with a goal of further expansion and extension of the mineralization at Nelligan, Philibert and Monster Lake, as we look to continue to grow the mineralization and advance a project that complements both the scale and timing of our Côté Gold Mine and its forthcoming expansion."

As a result of the completion of the Transaction and the acquisition by IAMGOLD of all of the NSUP Shares, Northern Superior became a wholly-owned subsidiary of IAMGOLD. Former Northern Superior shareholders are now entitled to receive, in exchange for each NSUP Share held immediately prior to the effective time of the Transaction, a combination of (i) 0.0991 of an IAMGOLD common share and (ii) C$0.19 in cash. The Transaction also included a concurrent distribution to Northern Superior's shareholders of all the common shares in the capital of ONGold Resources Ltd. previously held by Northern Superior. Full details of the Transaction are included in Northern Superior's management information circular dated November 10, 2025, which can be found under Northern Superior's profile on SEDAR+ at www.sedarplus.ca. The NSUP Shares will be delisted from the TSX Venture Exchange and an application will be made for Northern Superior to cease to be a reporting issuer in Ontario, British Columbia, Alberta and Quebec.

About IAMGOLD

IAMGOLD is an intermediate gold producer and developer based in Canada with operating mines in North America and West Africa, including Côté Gold (Canada), Westwood (Canada) and Essakane (Burkina Faso). The Côté Gold Mine achieved full nameplate in June 2025 and has the potential to be among the largest gold mines in Canada. IAMGOLD operates Côté Gold in partnership with Sumitomo Metal Mining Co. Ltd. In addition, the Company has an established portfolio of early stage and advanced exploration projects within high potential mining districts, including the Nelligan Mining Complex located in Quebec, Canada. IAMGOLD employs approximately 3,700 people and is committed to maintaining its culture of accountable mining through high standards of Environmental, Social and Governance practices. IAMGOLD is listed on the New York Stock Exchange (NYSE: IAG) and the Toronto Stock Exchange (TSX: IMG).

CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING INFORMATION

All information included in this news release, including any information as to the Company's vision, strategy, future financial or operating performance and other statements that express management's expectations or estimates of future performance or impact, including statements in respect of 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", "would", "could", "continue", "expect", "budget", "aim", "can", "focus", "forecast", "anticipate", "estimate", "maintain", "believe", "intend", "plan", "schedule", "guidance", "outlook", "potential", "seek", "targets", "cover", "strategy", "during", "ongoing", "subject to", "future", "objectives", "opportunities", "committed", "prospective", "likely", "progress", "strive", "sustain", "effort", "extend", "remain", "pursue", "predict", 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 heading "About IAMGOLD", and include, but are not limited to, statements with respect to the delisting of the NSUP Shares, Northern Superior ceasing to be a reporting issuer, the anticipated benefits from integrating Northern Superior and its assets, and the expansion and extension of the mineralization at Nelligan.

The Company cautions the reader that forward-looking statements are necessarily based upon a number of estimates and assumptions that, while considered reasonable by management, are inherently subject to significant business, financial, operational and other risks, uncertainties, contingencies and other factors, including those described below, which could cause actual results, performance or achievements of the Company to be materially different from results, performance or achievements expressed or implied by such forward-looking statements and, as such, undue reliance must not be placed on them. Forward-looking statements are also based on numerous material factors and assumptions, including as described in this news release, including with respect to: the Company's present and future business strategies; operations performance within expected ranges; anticipated future production and cash flows; local and global economic conditions and the environment in which the Company will operate in the future; the price of precious metals, other minerals and key commodities; projected mineral grades; international exchanges rates; anticipated capital and operating costs; the availability and timing of required governmental and other approvals for the construction of the Company's projects.

Risks, uncertainties, contingencies and other factors that could cause actual results, performance or achievements of the Company to be materially different from results, performance or achievements expressed or implied by such forward-looking statements include, without limitation: the Company's business strategies and its ability to execute thereon; the development and execution of implementing strategies to meet the Company's sustainability vision and targets; security risks, including civil unrest, war or terrorism and disruptions to the Company's supply chain and transit routes as a result of such security risks, particularly in Burkina Faso and the Sahel region surrounding the Company's Essakane mine; the availability of labour and qualified contractors; the availability of key inputs for the Company's operations and disruptions in global supply chains; the volatility of the Company's securities; litigation; contests over title to properties, particularly title to undeveloped properties; mine closure and rehabilitation risks; the lack of availability of insurance covering all of the risks associated with a mining company's operations; unexpected geological conditions; competition and consolidation in the mining sector; the profitability of the Company being highly dependent on the condition and results of the mining industry as a whole, and the gold mining industry in particular; changes in the global prices for gold, and commodities used in the operation of the Company's business (including, but not limited to diesel, fuel oil and electricity); legal, litigation, legislative, political or economic risks and new developments in the jurisdictions in which the Company carries on business, including the imposition of tariffs by the United States on Canadian products; changes in taxes, including mining tax regimes; the failure to obtain in a timely manner from authorities key permits, authorizations or approvals necessary for transactions, exploration, development or operation, operating or technical difficulties in connection with mining or development activities, including geotechnical difficulties and major equipment failure; the availability of capital; the level of liquidity and capital resources; access to capital markets and financing; the Company's level of indebtedness; the Company's ability to satisfy covenants under its credit facilities; changes in interest rates; adverse changes in the Company's credit rating; the Company's choices in capital allocation; effectiveness of the Company's ongoing cost containment efforts; the Company's ability to execute on de-risking activities and measures to improve operations; availability of specific assets to meet contractual obligations; risks related to third-party contractors, including reduced control over aspects of the Company's operations and/or the failure and/or the effectiveness of contractors to perform; risks arising from holding derivative instruments; changes in U.S. dollar and other currency exchange rates or gold lease rates; capital and currency controls in foreign jurisdictions; assessment of carrying values for the Company's assets, including the ongoing potential for material impairment and/or write-downs of such assets; the speculative nature of exploration and development, including the risks of diminishing quantities or grades of reserves; the fact that reserves and resources, expected metallurgical recoveries, capital and operating costs are estimates which may require revision; the presence of unfavourable content in ore deposits, including clay and coarse gold; inaccuracies in life of mine plans; failure to meet operational targets; equipment malfunctions; information systems security threats and cybersecurity; laws and regulations governing the protection of the environment (including greenhouse gas emission reduction and other decarbonization requirements; the uncertainty surrounding the interpretation of omnibus Bill C-59 and the related amendments to the Competition Act (Canada); employee relations and labour disputes; the maintenance of tailings storage facilities and the potential for a major spill or failure of the tailings facilities due to uncontrollable events, lack of reliable infrastructure, including access to roads, bridges, power sources and water supplies; physical and regulatory risks related to climate change; unpredictable weather patterns and challenging weather conditions at mine sites; disruptions from weather related events resulting in limited or no productivity such as forest fires, severe storms, flooding, drought, heavy snowfall, poor air quality, and extreme heat or cold; attraction and retention of key employees and other qualified personnel; availability and increasing costs associated with mining inputs and labour, negotiations with respect to new, reasonable collective labour agreements and/or collective bargaining agreements may not be agreed to; the ability of contractors to timely complete projects on acceptable terms; the relationship with the communities surrounding the Company's operations and projects; indigenous rights or claims; illegal mining; the potential direct or indirect operational impacts resulting from external factors, including infectious diseases, pandemics, or other public health emergencies; the completion of the transaction with Mines d'Or Orbec Inc., including the satisfaction of the conditions precedent to the proposed arrangement, and the inherent risks involved in the exploration, development and mining business generally. Please see the Company's Annual Information Form available on SEDAR+ at www.sedarplus.ca or Form 40-F available on EDGAR at www.sec.gov/edgar for a comprehensive discussion of the risks faced by the Company and which may cause actual results, performance or achievements of the Company to be materially different from results, performance or achievements expressed or implied by forward-looking statements.

Although the Company has attempted to identify important factors that could cause actual results to differ materially from those contained in forward-looking statements, there may be other factors that cause results not to be as anticipated, estimated or intended. The Company disclaims any intention or obligation to update or revise any forward-looking statements whether as a result of new information, future events or otherwise except as required by applicable law.

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