2021 FINA World Swimming Championships (25 m) – Men's 4 × 100 metre medley relay

The Men's 4 × 100 metre medley relay at the 2021 FINA World Swimming Championships (25 m), held in Abu Dhabi, United Arab Emirates, was a swimming event where teams of four male swimmers competed. Each swimmer in the relay swam a different stroke over a 100-metre distance, following the order of backstroke, breaststroke, butterfly, and freestyle. The event is part of the short course world championships, contested in a 25-meter pool. National teams from around the world participated, aiming to win medals and set new championship or world records. The race involved strategic team selection, considering each swimmer's specialty and performance level in their respective stroke. The overall time of the relay team determined the final standings and medal winners.