Gabriel Marie 'Gai' Waterhouse (nee Smith; born 2 September 1954) is an Australian horse trainer and businesswoman. After graduating from the University of New South Wales, she worked as an actor for a time, appearing in both Australian and English television series. Having worked under her father, TJ Smith, for a period of 15 years, Waterhouse was granted an Australian Jockey Club licence in 1992, and trained her first Group One winner later that year.In 1994, after her father became ill, she took over his Tulloch Lodge stable, and she has since trained over 100 G1 winners and won seven Sydney trainers' premierships. She was also the trainer of Fiorente, the winner of the 2013 Melbourne Cup, becoming the second woman (and first Australian woman) to train a winner of that race. Waterhouse was inducted into the Australian Racing Hall of Fame in 2007, and has been described as the 'first lady of Australian racing'.