Thor Nielsen (born 11 July 1959) is a Danish sprint and marathon canoeist who competed from the mid-1980s to the late 1990s. He won five medals at the ICF Canoe Sprint World Championships with two golds (K-1 10000 m: 1993, K-2 1000 m: 1994), two silvers (K-1 1000 m: 1993, K-2 10000 m: 1987), and a bronze (K-4 10000 m: 1985).
Nielsen also competed in two Summer Olympics, earning his best finish of sixth twice (K-2 500 m: 1992, K-2 1000 m: 1996).
Nielsen is currently working as the national coach of Denmark