The swimming competitions at the 2021 SEA Games took place at Mỹ Đình Aquatics Center in Hanoi, Vietnam from 14 to 19 May 2022.

[1] It is one of four aquatic sports at the Games, along with diving, finswimming and canoeing.

During the 4 × 100 m men freestyle relay event, both Singapore and Malaysia teams were disqualified by officials on technicalities shortly after winning gold and silver respectively.

Malaysia team coach Chris Martin said one of the Malaysian swimmers had entered the pool 0.12 s early during a changeover at the block.

[4] As a result, Vietnam, Indonesia and Thailand were awarded the gold, silver and bronze medals respectively.