The men's 100 metre butterfly competition of the swimming event at the 2015 SEA Games was held on 9 June at the OCBC Aquatic Centre in Kallang, Singapore.

[1] Prior to this competition, the existing Asian and Games records were as follows: The following records were established during the competition: All times are Singapore Standard Time (UTC+08:00) The heats were held on 9 June.

Heat 1 was held on 9 June.

Heat 2 was held on 9 June.

The final was held on 9 June.