| Lennart Mathiasen | |
| Nationality: | Danish |
| Birth Place: | Copenhagen, Denmark |
| Height: | 185 cm |
| Weight: | 80 kg |
| Country: | Denmark |
| Sport: | Sprint Canoeing |
Lennart Mathiasen (born 11 April 1948) is a Danish sprint canoeist who competed in the early 1970s. He was eliminated in the repechages of the C-2 1000 m event at the 1972 Summer Olympics in Munich.