Addison Gardner Foster (January 28, 1837 - January 16, 1917) was a United States Senator from Washington. Born in Belchertown, Massachusetts, he attended the common schools and moved to Wabasha County, Minnesota where he engaged in the grain and real estate business. He was auditor and surveyor of Wabasha County; he then moved to St. Paul, Minnesota in 1873 where he engaged in the lumber business. He moved to Tacoma, Washington in 1888 and continued in the lumber business, and also engaged in coal mine operations and railroad construction.
Gardner was elected as a Republican to the U.S. Senate and served from March 4, 1899, to March 3, 1905; he was not a candidate for reelection. While in the Senate, he was chairman of the Committee on Coast and Insular Survey (Fifty-sixth and Fifty-seventh Congresses) and a member of the Committee on Geological Survey (Fifty-eighth Congress). He resumed the lumber business at Tacoma, and in 1914 retired from active business pursuits and resided in Tacoma until his death in 1917; interment was in Tacoma Cemetery.