Sun Stream (1942–January 1959) was a British Thoroughbred racehorse and broodmare, best known for winning two Classics in 1945. The filly won five times from seven races in a track career which lasted from spring 1944 until June 1945. As a two-year-old in 1944 she won three races including the Queen Mary Stakes. After being beaten on her three-year-old debut she won the 1000 Guineas over one mile at Newmarket and a substitute Oaks over one and a half miles at the same course a month later.