Kansas, North Carolina, Virginia and Oregon were revealed as the top seeds for the NCAA men's basketball tournament known as March Madness that begins on Thursday. 

Oregon was the biggest surprise to receive a No. 1 seed, beating out Michigan State for a spot on the top line.

The Spartans were widely viewed as a top seed, and their win over Purdue in the Big Ten tournament final did nothing to hurt their resume.

The Jayhawks (30-4) are the overall No. 1. They won both the regular-season and conference titles in the nation's toughest league, the Big 12.

Oregon's surprise was in keeping with one of the most unpredictable seasons ever. The top spot in The Associated Press poll changed hands six times, one short of the record.

A supposedly leaked official bracket was posted on Twitter during the CBS selection show. It ended up being 100 per cent correct and It was nearly an hour later by the time the network had officially announced all the teams

South Region

Kansas earned the top overall seed and opens play in the South Region against 16-seed Austin Peay on Thursday.

The Jayhawks won the Big 12 regular-season and tournament titles. They're chasing a second national title under Bill Self.

Villanova, one of six teams to hold the No. 1 ranking in the Top 25 this year, is the No. 2 seed in the region. The region also features a First Four matchup between Vanderbilt and Wichita State for the 11th seed.

West Region

Coming off a sweep of the Pac-12 regular-season and tournament titles, eighth-ranked Oregon (28-6) is the top seed in the West Region and will play in Spokane against the winner between Holy Cross and Southern in the First Four.

The Ducks made a surprising run to last year's Pac-12 title game, setting the stage for their breakout season this year.

Oregon won the Pac-12 regular-season title by a game over Utah and ran the 12th-ranked Utes off the court in Las Vegas, rolling to an 88-57 victory that punctuated the Ducks' bid for a No. 1 seed. Oklahoma is the No. 2 seed.

East Region

The Tar Heels (28-6) won the ACC Tournament and open against the Florida Gulf Coast-Fairleigh Dickinson winner about 30 miles away from campus in Raleigh, N.C.

North Carolina won its 18th ACC championship, one shy of Duke's conference record. The Tar Heels played tournament games in Raleigh in 2008, and rolled to two easy wins in the opening weekend on their way to the Final Four. The Tar Heels won their last national championship in 2009.

Xavier earned the No. 2 seed, followed by West Virginia, Kentucky and Indiana.

Florida Gulf Coast is back in the tournament for the second time in program history and first since it reached the Sweet 16 in 2013. The East Regional final is March 27 in Philadelphia, with the winner advancing to the Final Four.

Midwest Region

Virginia is a No. 1 seed even without a conference title this season.

The Cavaliers (26-7) are the top team in the Midwest Region, and will play Mid-Eastern Conference champion Hampton (21-10) in their tournament opener Thursday in Raleigh, North Carolina.

After finishing the ACC regular season a game behind North Carolina, the Cavaliers advanced to the tournament championship game and lost to the Tar Heels 61-57 on Saturday.

Michigan State (29-5), which won the Big Ten tournament championship earlier Sunday, is the No. 2 seed in the Midwest Region.

While an ACC runner-up, Virginia had some impressive non-conference wins. There was a three-game stretch in December when the Cavaliers beat No. 9 West Virginia, No. 3 Villanova and No. 24 California.