Sir Robert Cosgrove KCMG (28 December 1884 – 25 August 1969) was an Australian politician who was the 30th and longest-serving Premier of Tasmania. He held office for over 18 years, serving from 1939 to 1947 and from 1948 to 1958. His involvement in state politics spanned five decades, and he dominated the Tasmanian branch of the Australian Labor Party for a generation.