John Ross Frederick Duncan (born 25 March 1944) was a former Australian cricketer who played one Test match in 1971.

Duncan was a right-arm fast-medium bowler. He was selected to play in the Fifth Test at Melbourne instead of participating in a different match during the 1970–71 Ashes series. He was chosen to replace the injured Graham McKenzie as a fast-medium seam bowler. In his first innings, he scored 3 runs with the bat and took 0 wickets for 30 runs with the ball. He did not bat or bowl in the second innings and did not take any catches. He was not selected for the Sixth Test, and Dennis Lillee was chosen instead. Duncan also played one match for Australia in 1971–72 against Gary Sobers’ Rest of the World XI, but he did not have success in that game.

From 1964–65 to 1970–71, Duncan played for Queensland, often bowling with Peter Allan. He later played for Victoria in 1971–72 and 1972–73. His best performance was taking 8 wickets for 55 runs and 5 wickets for 70 runs against Victoria at Melbourne in December 1970.