Michael Sim (born 23 October 1984) is an Australian professional golfer.
Sim was born in Aberdeen, Scotland, and moved to Australia when he was 5 years old. He was the top ranked amateur in the world in 2005 having won four titles during the year including the Sunnehanna Amateur, which boasts major winners Ben Crenshaw and Tommy Aaron amongst its list of former champions. He turned professional at the end of the year.
Sim played on the Nationwide Tour in 2006, and qualified for the PGA Tour by virtue of a 19th place finish on the end of season money list, aided by a win at PalmettoPride Classic. After a late start to the 2007 season, caused by a stress fracture of the spine, he finished 169th on the PGA Tour money list. He was granted a medical extension for 2008, but failed to win enough money in five events to retain his place on the PGA Tour, and he returned to the second tier Nationwide Tour. In April 2009, Sim's bid to return to the elite tour got off to a good start when he secured his second career victory at the Stonebrae Classic, finishing six strokes clear of the field. The following week he finished in second after losing in a playoff to Patrick Sheehan, and then in May he won the BMW Charity Pro-Am in a playoff over Fabián Gómez.