Highlights:

• Work now underway on the Stonesthrow Copper-Gold Project in Saskatchewan
• Drilling is underway on the Esmeralda County Gold Project, situated within the Walker Lane trend, one of the most prolific gold-producing corridors in North America
• Sienna's maiden drill program on the project, and the Company's first drill program of 2026
• Strong share structure with just over 40 million shares outstanding and strong cash position support multiple expected work programs and marketing initiatives through the second half of 2026

Vancouver, British Columbia--(Newsfile Corp. - October 5, 2026) - Sienna Resources Inc. (TSXV: SIEN) (OTCID: SNNAF) (WKN: A418KR) (the "Company" or "Sienna") is pleased to announce that the work program on the 31,718-acre Stonesthrow Project, prospective for gold, silver, and copper, in Saskatchewan is now underway. Ground crews have been dispatched to specific targeted locations for a more detailed groundwork over the highest priority targets uncovered by the recently completed airborne work.

Jason Gigliotti, President of Sienna Resources Inc., stated, "We are continuing to be very active on our projects right now. When you couple this ground program to focus on the highest priority targets with the current gold drill program we have going on our Esmeralda County Gold Project within the Walker Lane trend in Nevada, it is clear this is a time of high potential impactful news drivers. The Walker Lane trend has a proven track record of hosting significant gold deposits, and this is our first opportunity to test the project with the drill bit. With our tight share structure and robust cash position, we believe any drilling success has the potential for an outsized impact on the Company. Being active on multiple work programs gives Sienna multiple opportunities for success the short term. Truly exciting times for Sienna shareholders."

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About Sienna

Sienna has multiple lithium assets in Nevada, which include the 100%-owned, 1,828-acre Elko Lithium Project and the 1,231-acre Cave Creek Lithium Project, both located in Elko County, Nevada, directly bordering and nearly surrounded by Surge Battery Metals' (NILI) Nevada North Lithium Project - the highest-grade lithium clay deposit in the USA. In Clayton Valley, Nevada, Sienna holds the 2,300-acre Deep Basin Lithium Brine JV, which has access to some of the deepest parts of the only lithium brine basin with active production in the USA. Also in Nevada, Sienna holds the 1,156-acre Esmeralda County Gold Project, situated within the Walker Lane trend. In Saskatchewan, Sienna holds the 31,718-acre Stonesthrow Project, prospective for gold, silver, and copper, located directly adjacent to Ramp Metals Inc.'s (RAMP) Rottenstone Project.

Qualified Person:

The technical contents of this release were reviewed and approved by Frank Bain, PGeo, independent to the Company and a qualified person as defined by National Instrument 43-101.

"Jason Gigliotti"
President
Sienna Resources Inc.

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

Forward-Looking Statements

This news release contains forward-looking statements and forward-looking information within the meaning of applicable Canadian securities legislation, including statements regarding the commencement and anticipated results of the drill program at the Esmeralda County Gold Project, and the Company's plans and expectations for its work programs in 2026. Forward-looking statements are based on the reasonable assumptions, estimates, analysis and opinions of management made in light of its experience and its perception of trends, current conditions and expected developments, as well as other factors that management believes to be relevant and reasonable in the circumstances at the date such statements are made, but which may prove to be incorrect. Actual results could differ materially from those anticipated due to a number of factors and risks, including risks inherent in mineral exploration. Readers are cautioned not to place undue reliance on forward-looking statements, and the Company disclaims any obligation to update or revise any forward-looking statements, except as required by applicable law.

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