Marion Michael "Mike" Rounds (born October 24, 1954) is an American politician. Rounds has served as the 31st and current Governor of South Dakota since January 7, 2003, having been elected on November 5, 2002 and re-elected on November 7, 2006. His term expires in January 2011.

Rounds, the eldest of eleven siblings, was born in Huron, South Dakota and has lived in Pierre, the state capital, since he was three years old. He was named for an uncle, Marion Rounds, who was killed in the Pacific theater during the Second World War.

Several members of the Rounds family have been involved in state government. His father, Don Rounds, worked at various times as state director of highway safety, a staffer for Rural Electrification Administration, and executive director of the South Dakota Petroleum Council. Rounds's brother, Tim Rounds, is a member of the South Dakota State Legislature representing District 24, which includes Pierre.