Scottie Reynolds hit a lay-up in traffic with 0.5 seconds left to provide the winning margin for the third seeded Villanova, who are hoping to win their first national championship since 1985.
"I got lucky with one tonight," Reynolds, who scored 15 points, told reporters. After the game he tracked down the ball as a keepsake.
Top seed Connecticut captured the West Region with a 82-75 victory over number three Missouri behind 23 points by reserve freshman guard Kemba Walker.
"This one was emotional," Connecticut coach Jim Calhoun said. "I'm going with a group now who found a way."
Aided by a second-half surge, Connecticut were able to avoid a potential comeback by the Tigers. The Huskies made just eight baskets in the second half.
"Everything starts with defense with this team," said guard A.J. Price, who scored 18 points.
The remaining two teams to make up the Final Four will be decided on Sunday when number one North Carolina face second-seeded Oklahoma in the final of the South Region and Midwest top seed Louisville battle number two Michigan State.
