Dennis John Trewin AO (born 14 August 1946) is an Australian former public servant, who was the Australian Statistician, the head of the Australian Bureau of Statistics, between July 2000 and January 2007. Trewin joined the ABS in 1966 as a statistics cadet. Between 1992 and 1995 he was the Deputy Government Statistician in Statistics New Zealand and a Deputy Australian Statistician from 1995 to 2000, when he was appointed as the Australian Statistician.