Swimming at the 2005 World Aquatics Championships – Men's 4 × 100 metre freestyle relay

The Men's 4×100 Freestyle Relay event at the 2005 FINA World Aquatics Championships was swum on July 24, 2005 in Montreal, Quebec, Canada. 24 teams swam in preliminary heats in the day's morning session, with the top-8 teams from the prelims advancing to swim again in the final heat in the day's evening session.

At the start of the event, the existing World (WR) and Championships (CR) records were:
 * WR: 3:13.17, South Africa (Schoeman, Ferns, Townsend, Neethling), swum August 15, 2004 in Athens, Greece
 * CR: 3:14.06, 🇷🇺 Russia (Kapralov, Usov, Pimankov, Popov), swum July 20, 2003 in Barcelona, Spain