The Men's 800 metre freestyle competition at the 2019 World Championships was held on 23 and 24 July 2019.

[1][2] The defending champion was Gabriele Detti, but he finished 5th in the final.

The champion, Gregorio Paltrinieri, was the defending bronze medalist.

Prior to the competition, the existing world and championship records were as follows.

[3] The final was held on 24 July at 20:02.