Oscar Sherman Gifford (October 20, 1842 - January 16, 1913) was an American lawyer of Canton, South Dakota. He served six years in the United States House of Representatives, first as the non-voting delegate from the Dakota Territory, then as a full member of the House from South Dakota.
Oscar was born in Watertown, Jefferson County, New York, and moved with his parents to Wisconsin, settling in Rock County and then in Brown County, Illinois. He served as a private in the Union during the American Civil War.
After the war Gifford studied law and was admitted to the bar in 1871, beginning his practice in Canton, Dakota Territory (now South Dakota). He was district attorney for Lincoln County, mayor of Canton, and a member of the State constitutional convention of South Dakota which convened at Sioux Falls on September 7, 1883. He was a Republican, and was twice elected as the Territorial delegate to Congress, and served from March 4, 1885 to March 3, 1889.
Upon the admission of South Dakota as a state he was elected as a Representative, serving from November 2, 1889 to March 3, 1891. He was a candidate for re-nomination in 1890, but lost and resumed the practice of law in Canton, where he died. He was interred in Forest Hill Cemetery in Canton.