Sovereign (sail number K-12) was the unsuccessful challenger of the 1964 America's Cup for the Royal Thames Yacht Club.
Designed by David Boyd and built by Alexander Robertson and Sons, Sovereign was built especially for the 1964 America's Cup challenge. This was the second post-war 12-metre yacht to be designed by David Boyd and built at Alexander Robertson and Sons, the first one being Sceptre.
Sovereign was built for J. A. Boyden in 1963. Sovereign lost 4-0 to defender Constellation of the New York Yacht Club.
- Alexander Robertson and Sons, history of the yard.