The Thousand Guineas is a Melbourne Racing Club Group 1 Thoroughbred horse race for three year old fillies at set weights run over a distance of 1600 metres at Caulfield Racecourse, Melbourne, Australia in early October.

This is a race contested by Australia's top fillies. The Thousand Guineas is held midweek on Wednesday, just ahead of the Caulfield Cup on Saturday. The male equivalent of the Thousand Guineas is the Caulfield Guineas, usually held on the weekend before.

First run in 1946 (Sweet Chime). Group 1 since 1979.

Notable winners include CHICQUITA (1949); TRUE COURSE (1950): WENONA GIRL (1960): BEGONIA BELLE (1967) won the Lightning Stakes (1968) and Newmarket Hep (1969); TOY SHOW
(1975): RIVERINA CHARM (1988): WHISKED (1990). dam ofTieThe Knot; ALINGHI (2004); MISS FINLAND (2006); and ATLANTIC JEWEL (2011).