Gerrit Jan 'Gert-Jan' Liefers (born 26 September 1978 in Apeldoorn, Gelderland) is a former Dutch middle distance runner, who came 8th in the 1500 m final at the 2004 Olympics. He was also a finalist in the same event in the 2001 and 2003 World Championships.
Liefers finished 8th in the 5000 m final at the 2006 European Athletics Championships in Gothenburg. He is the Dutch record holder at 1500 m, the mile and 3000 m.