Ouassim Oumaiz (born 30 March 1999) is a Spanish long-distance runner.

He is the Spanish national record holder in the 5km road race with a time of 13:19, which he set in 2020 at the Seven Hills 5K Invitational.

[1] He also won the Cross de Atapuerca cross-country race in 2019.

During his successful 2023 season, Oumaiz set a personal best and Andalusian record in the 5,000 m to gain a spot representing Spain at the 2023 World Athletics Championships.

[2] However, in March 2024, news broke that Oumaiz had tested positive for a banned substance, GHRP-2, during a routine anti-doping test.