Robert Allenby (born 12 July 1971) is an Australian professional golfer.

Allenby was born in Melbourne, Australia. His father was from Leeds, England and emigrated to Australia as a young man. He turned professional in 1992 and was soon successful, topping the PGA Tour of Australasia Order of Merit in his first season and again in 1994. He continues to play some events on his home tour and has won 12 events on it, including one as an amateur. He also began to play on the European Tour and it was his principal tour until 1998. He won four tournaments on it, including three in 1996, when he finished third on the Order of Merit. He has featured in the top 10 of the Official World Golf Rankings.

Allenby now plays primarily in the U.S. on the PGA Tour. He earned exempt status for 1999 by finishing 17th at the 1998 Qualifying School. He had a disappointing first season in America, coming 126th on the money list, but came good in 2000 when he won the Shell Houston Open and the Advil Western Open. He claimed another pair of wins the following season. In both of those years he came 16th on the money list. He has not won since but finished in the top 50 each year from 2002-2004. His performances in the major championships have been somewhat disappointing; his highest placing in a major is tied seventh at the 2004 U.S. Open.