South Dakota Amendment C of 2006 is an amendment to the South Dakota Constitution to make it unconstitutional for the state to recognize or perform same-sex marriages, or to recognize civil unions, domestic partnerships, or other quasi-marital relationships regardless of gender. The referendum was approved on 7 November 2006 by 52% of the state's voters.
The text of the adopted amendment states: <blockquote>Only marriage between a man and a woman shall be valid or recognized in South Dakota. The uniting of two or more persons in a civil union, domestic partnership, or other quasi-marital relationship shall not be valid or recognized in South Dakota.</blockquote>
The amendment was rendered void by Obergefell v. Hodges, a US Supreme Court decision that legalized same-sex marriage nationwide.
On January 24, 2005, the South Dakota House of Representatives passed, by a vote of 53 in favor and 16 against, South Dakota House Joint Resolution 1001 (SD HJR 1001). On February 14, 2005, the South Dakota Senate passed, by a vote of 20 in favor and 15 against, HJR 1001, which put it on the ballot for the 2006 general election.
On November 7, 2006, at 7:00 PM CT, polls closed thought the entire state of South Dakota. Between 9:00 PM and 11:00 PM CST, Amendment C was projected to pass.