Sioux Kingsbury Grigsby (December 25, 1873 – August 21, 1968) was an attorney and politician in the United States state of South Dakota. Grigsby was born into a prominent pioneering family, Kingsbury family in South Dakota and set up a law practice which he would maintain for over 60 years. Grigsby served as state representative, state senator, and Lieutenant Governor of South Dakota from 1945 to 1949.