| Birth Place: | Bükkaranyos, Hungary |
| Height: | 1.76m (05.77feet) |
| Weight: | 69kg (152lb) |
| Sport: | Athletics |
| Event: | 5000 m, 10,000 m, marathon |
| Club: | Salgótarjáni BTC |
| Pb: | 5000 m – 13:29.2 (1968) 10000 m – 28:27.0 (1966) Marathon – 2:17:59 (1969) |
| Show-Medals: | yes |
Lajos Mecser (born 23 September 1942) is a retired Hungarian long-distance runner who won two European championships medals in 1966–67. He competed in the 5000 m at the 1964 Olympics and in the 10,000 m and marathon at the 1968 Olympics with the best result of 23rd place in the 10,000 m.