The 2003 Big Ten men's basketball tournament was the postseason men's basketball tournament for the Big Ten Conference and played between March 13 and March 16, 2003 at United Center in Chicago, Illinois.

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

All Big Ten schools played in the 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.