David Realista Grachat (born 21 January 1987) is a Portuguese para-swimmer, competing in S9 classification events.

Grachat has won medals at both European and World level, and specializes in the 400m freestyle.

[1] Grachat made his Paralympic debut at the 2008 Games in Beijing competing in the 50 m and 100 m freestyle S9 events and the 200 m individual medley (SM9).

Grachat's first international success came in his favoured 400 m freestyle at the 2014 IPC Swimming European Championships in Eindhoven.

[1] In the buildup to the 2016 Summer Paralympics in Rio, Grachat competed at the 2016 IPC Swimming European Championships, held on home soil in Funchal.