MacGuyver Dean Greyling (born 1 January 1986) is a rugby union footballer who represents South Africa in international rugby, and the Blue Bulls in the Currie Cup and Super Rugby. He was educated at Afrikaanse Hoër Seunskool.
Greyling was one of the stars of the 2004 Craven Week competition, and represented the Blue Bulls' age-group teams from 2005 to 2007. He made his Super Rugby debut for the franchise in 2008. In October 2010, Greyling was selected to the Springbok squad of 39 players to prepare for the November tour of Europe.
Greyling made his Springbok debut in the starting line-up against Australia on 23 July 2011 in Sydney. He played his second test for his country the following week against the All Blacks in Wellington. He was not selected for the 2011 Rugby World Cup.
He played in his last test (from the bench) on 15 September 2012 against New Zealand in Dunedin, but after receiving a yellow card for foul play in the 64th minute, was not selected again for the Springboks during 2012.