The Men's 100 metre breaststroke competition at the 2019 World Championships was held on 21 and 22 July 2019.

[1][2] Adam Peaty broke the world record with a time of 56.88 in the semi-final, the first man to swim under 57 seconds in this event,[3] and went on to win in the final.

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

The following new records were set during this competition.

[5] The semifinals were held on 21 July at 20:51.