Saint Mary's captured its second West Coast major powerhouse and 24th-ranked Gonzaga, 78-74, in overtime.
Gonzaga's Elias Harris made a layup and three-pointer in the final 15 seconds of regulation to send the WCC final to overtime, where Matthew Dellavedova made the go-ahead free throws with 39.3 seconds remaining.
The top-seeded Gaels (27-5), who snapped Gonzaga's string of 11 straight regular season conference titles this year, were able to hold on in the extra session and cut down the nets at Orleans Arena.
Dellavedova finished with 22 points, Rob Jones added 18 points and nine rebounds and Jorden Page netted 16 for the conference champs.
Harris' 22 points and 13 rebounds went for naught, as the second-seeded Bulldogs (25-6) shot just 5-of-22 (23 percent) from three-point range to fall short.
Gonzaga freshman Kevin Pangos shot just 3-of-18 from the field and finished with just seven points -- half of his season average.
Late in overtime, Pangos missed a straightaway three-pointer with the score tied, 72-72, then was whistled for a loose ball foul going after the rebound.
Dellavedova, the WCC Player of the Year, drained the ensuing free throws with 39.3 seconds showing. Sam Dower missed a turnaround hook shot from the left block at the other end, and Page and Dellavedova each had two successful trips at the foul line to seal the Gaels' tourney crown.
The extra session was only made necessary because Harris cleaned up a Pangos miss with a layup with 15 seconds to play, then hit an NBA-range three-pointer after Gonzaga forced a jump ball on the inbounds pass.
The trey went through with 3.7 seconds remaining, and Dellavedova's runner from the right side was a little too long as the buzzer sounded.
The score was fittingly tied at halftime, 36-36, and neither team led by double digits after the break.
The Gaels captured their first outright conference championship since 1989 to earn the top seed...The Bulldogs' appearance in Monday's game set a new NCAA record, as it was their 15th straight appearance in a conference championship...The rivals split the regular season series against each other.