Swimming at the 2013 World Aquatics Championships – Men's 800 metre freestyle

The men's 800 metre freestyle event in swimming at the 2013 World Aquatics Championships took place on 30–31 July at the Palau Sant Jordi in Barcelona, Spain.

Records
Prior to this competition, the existing world and championship records were:

Heats
The heats were held at 10:54.

Final
The final was held at 19:29.