Rebecca Craighill Lancefield (January 2, 1895 – March 1, 1981) was a prominent American microbiologist. She joined the Rockefeller Institute for Medical Research in New York in 1918, and was associated with that institute throughout her long and outstanding career. Her bibliography comprises more than 50 publications published over 60 years. Her main achievements lie in her work on group A streptococci and their association with rheumatic fever.