The 2005 Big Ten men's basketball tournament was the postseason men's basketball tournament for the Big Ten Conference and was played between March 9 and 12, 2005, at the United Center in Chicago, Illinois.

This was the eighth annual Big Ten Men's Basketball Tournament.

As a result, Illinois received the Big Ten's automatic bid to the NCAA tournament.

Teams were seeded by conference record, with a tiebreaker system used to seed teams with identical conference records.

Seeding for the tournament was determined at the close of the regular conference season.