6-K

UNITED STATESSECURITIES AND EXCHANGE COMMISSIONWashington, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER PURSUANT TO RULE 13a-16 OR 15d-16 UNDERTHE SECURITIES EXCHANGE ACT OF 1934

For the month of October 2025

Commission File Number: 001-40786

Sigma Lithium Corporation

(Translation of registrant's name into English)

181, Bay Street, Suite 4400Toronto, Ontario, M5J 2T3, Canada

(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Form 20-F [   ]      Form 40-F [ X ]

EXHIBIT INDEX

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

	Sigma<br> Lithium Corporation
	(Registrant)
Date: October 17, 2025
	Ana Cristina Cabral Gardner
	Chief Executive Officer

Exhibit 99.1

SIGMA LITHIUM ADDED TO MORGAN STANLEY NATIONALSECURITY INDEX

SÃO PAULO, Oct. 16, 2025 - Sigma Lithium Corporation (NASDAQ: SGML), a leading global lithium producer dedicated to powering the next generation of batteries for electric vehicles and energy storage systems with socially and environmentally sustainable lithium concentrate, announces today that the company´s US-listed shares (NASDAQ:SGML) have been added to the Morgan Stanley National Security Stock Index (Bloomberg: MSXXNSEC).

The Morgan Stanley National Security Index is a thematic equity index developed by Morgan Stanley to track publicly listed companies whose operations, products or technologies contribute to national security, supply chain resilience and strategic infrastructure. The index includes leading US-listed firms engaged in several activities connected to technologies across industries such as defense, battery materials, cybersecurity, energy (including nuclear) reflecting the importance of these industrial complexes.

In addition to Sigma Lithium, the index includes other leading US-listed producers of strategic materials such as Albermarle (lithium), Freeport-McMoRan (copper), First Quantum Minerals (copper), Cameco Corp (uranium), MP Materials (rare earths), Lithium Americas (lithium), Centrus Energy Corp (uranium), NioCorp Developments (rare earths), USA Rare Earth (rare earths), Ivanhoe Electric (rare earths), among others. The index also includes Tesla (technology, batteries).

ABOUT SIGMA LITHIUM

Sigma Lithium (NASDAQ: SGML, TSXV: SGML, BVMF: S2GM34) is a leading global lithium producer dedicated to powering the next generation of batteries for electric vehicles and energy storage systems with carbon neutral, socially and environmentally sustainable chemical-grade lithium concentrate.

The Company operates one of the world’s largest lithium production sites—the fifth-largest industrial-mineral complex for lithium oxide—at its Grota do Cirilo Operation in Brazil. Sigma Lithium is at the forefront of environmental and social sustainability in the battery materials supply chain, producing Quintuple Zero Green Lithium: made with zero carbon, zero coal power, zero tailings dams, zero utilization of potable water and zero use of hazardous chemicals.

Sigma Lithium currently produces 270,000 tonnes of lithium oxide concentrate on an annualized basis (approximately 38,000–40,000 tonnes of LCE) at its state-of-the-art Greentech Industrial Lithium Plant. The Company is now constructing a second plant to double production capacity to 520,000 tonnes of lithium oxide concentrate (approximately 77,000–80,000 tonnes of LCE).

For more information about Sigma Lithium, visit our website (https://sigmalithiumresources.com/)

FOR ADDITIONAL INFORMATION PLEASE CONTACT

Anna Hartley, Vice President Investor Relations

anna.hartley@sigmalithium.com.br

Sigma Lithium

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FORWARD-LOOKING STATEMENTS

This news release includescertain “forward-looking information” under applicable Canadian and U.S. securities legislation, including but not limitedto statements relating to timing and costs related to the general business and operational outlook of the Company, the environmental footprintof tailings and positive ecosystem impact relating thereto, donation and upcycling of tailings, timing and quantities relating to tailingsand Green Lithium, achievements and projections relating to the Zero Tailings strategy, achievement of ramp-up volumes, production estimatesand the operational status of the Grota do Cirilo Project, and other forward-looking information. All statements that address future plans,activities, events, estimates, expectations or developments that the Company believes, expects or anticipates will or may occur is forward-lookinginformation, including statements regarding the potential development of mineral resources and mineral reserves which may or may not occur.Forward-looking information contained herein is based on certain assumptions regarding, among other things: general economic and politicalconditions; the stable and supportive legislative, regulatory and community environment in Brazil; demand for lithium, includingthat such demand is supported by growth in the electric vehicle market; the Company’s market position and future financial and operatingperformance; the Company’s estimates of mineral resources and mineral reserves, including whether mineral resources will ever bedeveloped into mineral reserves; and the Company’s ability to operate its mineral projects including that the Company will not experienceany materials or equipment shortages, any labour or service provider outages or delays or any technical issues. Although management believesthat the assumptions and expectations reflected in the forward-looking information are reasonable, there can be no assurance that theseassumptions and expectations will prove to be correct. Forward-looking information inherently involves and is subject to risks and uncertainties,including but not limited to that the market prices for lithium may not remain at current levels; and the market for electric vehiclesand other large format batteries currently has limited market share and no assurances can be given for the rate at which this market willdevelop, if at all, which could affect the success of the Company and its ability to develop lithium operations. There can be no assurancethat such statements will prove to be accurate, as actual results and future events could differ materially from those anticipated insuch statements. Accordingly, readers should not place undue reliance on forward-looking information. The Company disclaims any intentionor obligation to update or revise any forward-looking information, whether because of new information, future events or otherwise, exceptas required by law. For more information on the risks, uncertainties and assumptions that could cause our actual results to differ fromcurrent expectations, please refer to the current annual information form of the Company and other public filings available under theCompany’s profile atwww.sedarplus.com.

Neither the TSX Venture Exchange nor its Regulation ServicesProvider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy ofthis news release.

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