Samuel Henry Piles (December 28, 1858 - March 11, 1940) was a United States Senator from Washington. Born near Smithland, Kentucky, he attended private schools there, and studied law. He was admitted to the bar and commenced practice in Snohomish, Territory of Washington in 1883. He moved to Spokane in 1886 and later in the same year to Seattle, where he engaged in the practice of law. He was assistant prosecuting attorney for the third judicial district of the Territory of Washington from 1887 to 1889 and was city attorney of Seattle, 1888-1889; he was also general counsel of the Pacific Coast Co. from 1895 to 1905.
In 1904, Piles was elected as a Republican to the U.S. Senate and served from March 4, 1905, to March 3, 1911. He was not a candidate for renomination in 1910. While in the Senate, he was chairman of the Committee on Coast and Insular Survey (Fifty-ninth through Sixty-first Congresses). He resumed the practice of law in Seattle, and was appointed by President Warren Harding as Envoy Extraordinary and Minister Plenipotentiary to Colombia, an office he held from 1922 to 1928. He retired from active pursuits and moved to Los Angeles, California, where he died in 1940; interment was in Lakeview Cemetery, Seattle.