The slam dunks, cheers, and, of course, the postgame parties — March Madness is officially here! As the NCAA teams battle it out over hoops, we're taking a look at all the celebs who cheer on their favorite teams courtside, as well as the cute couples showing PDA on the Kiss Cam . Whether it's Katie Holmes  jumping up with joy for the NY Knicks, Justin Timberlake  cheering on the LA Lakers, Mary Kate and Ashley Olsen  sitting on the edge of their seats at Madison Square Garden, or Ashton Kutcher  celebrating with Mila Kunis , stars love to feel the basketball spirit from the sidelines. See celebs hanging out, drinking beer, and checking out the cheerleaders when you scroll down!
If you'd rather ogle the guys than fill out a bracket, check out 28 hot college players  or get in on our March Man-ness  fun by voting for your favorite star.
Katie Holmes  couldn't contain her excitement after a big moment in the Miami Heat vs. New York Knicks game in January.
Jake Gyllenhaal  felt the LA Lakers spirit with pals when the team played the Minnesota Timberwolves in November 2013.
Ben Stiller  and Drake made an unlikely courtside couple during a NY Knicks game in April 2013.
Mila Kunis  and Ashton Kutcher  checked out the Lakers game together in February 2013.
Former President Bill Clinton got in the zone during a Oklahoma City Thunder vs. Brooklyn Nets game in January.
David Beckham  and Victoria Beckham  showed PDA during a Lakers game in May 2012.
Joseph Gordon-Levitt clapped on as the LA Lakers competed against the Oklahoma City Thunder.
Rihanna  brought her brother, Rajad Fenty, to see the LA Lakers battle it out with the Portland Trail Blazers in December 2013.
Kate Hudson  took in a Lakers game with her brother Oliver in November 2008.
Jay Z shared an adorable moment with his godson at a Brooklyn Nets game in April — their mutual excitement made for one sweet photo!
John Legend  and Chrissy Teigen looked cute in the stands while watching the Lakers play the Brooklyn Nets in February 2013.
Kim Kardashian  and Kanye West  looked stylish while sitting courtside at the May 2012 playoff game between the LA Lakers and the Denver Nuggets.
Joseph Gordon-Levitt cheered on the LA Lakers with his dad, Dennis, in January 2013.
Eva Longoria  sat courtside with Kevin Costner  and her stylist, Robert Verdi, while watching the NY Knicks play the Dallas Mavericks in February 2012.
Selena Gomez  and Justin Bieber  sat front row as the Lakers played the San Antonio Spurs in April 2012.
Vanessa Hudgens  and Josh Hutcherson cheered on the LA Lakers as they played the New Orleans Hornets in March 2011.
Ashley and Mary-Kate Olsen  sported shades and smiles during a NY Knicks game in May 2013.
Then-couple Pete Wentz  and Ashlee Simpson  showed PDA at a NY Knicks game in February 2010.
Things got serious for Mark Wahlberg  and Matt Damon  as they watched their hometown team, the Boston Celtics, play in the NBA Finals in June 2008.
Spike Lee and company could not hold back their enthusiasm during a NY Knicks playoff game in May 2013.
Double high five! Ben Stiller  and Jason Sudeikis shared an enthusiastic moment as the NY Knicks played the Boston Celtics in May 2013.
Andrew Garfield took in a NY Knicks game with a friend in May 2013.
Denzel Washington  and 50 Cent shared a laugh while sitting courtside at an LA Lakers game in April 2013.
Jack Nicholson  and Adam Sandler  seemed to have a serious conversation in the stands at a January 2013 Lakers game.
Katie Holmes  attended a NY Knicks game with her agent, Adam Schweitzer, in February 2013.
Fergie  took in a Lakers game with her Black Eyed Peas bandmate Will.i.am in November 2009.
Anna Wintour sat front row with Liev Schreiber  at a NY Knicks game in February 2011.
Kate Upton sported a foam finger to support the NY Knicks as they played the Miami Heat in May 2012.
Zac Efron  had fun hanging with the cheerleaders at an LA Lakers game in April 2011.
Vanessa Hudgens  and Austin Butler were seated near Anna Wintour during a game at Madison Square Garden in December 2012.
Katie Couric got silly for the camera during a NY Knicks playoff game in May 2013.
David Beckham  clowned around courtside with his sons Cruz and Romeo during a Lakers game in November 2012.
Khloé Kardashian and Nicole Richie  goofed around in the stands during a January 2011 Lakers game.
Jessica Alba  and Cash Warren watched the NY Knicks play the Cleveland Cavaliers in March 2011.
Justin Timberlake  and Jessica Biel  cheered on the Lakers during the NBA playoffs in May 2012.
Drew Barrymore  planted a kiss on her husband, Will Kopelman, as they sat courtside at a NY Knicks game in January.
Will Smith  repped his hometown team, the Philadelphia 76ers, while watching them play the Miami Heat with his wife, Jada Pinkett Smith , in March 2012.
Tom Brady  and Gisele Bündchen ate popcorn while watching the Boston Celtics play in May 2008.
Julianne Hough and Ryan Seacrest  sat courtside to watch the Lakers play the Golden State Warriors in October 2010.
Cameron Diaz  caught a basketball during a game between the LA Lakers and the Cleveland Cavaliers in January 2011.
Alicia Keys  and Swizz Beatz posed for a sweet family photo with their son, Egypt, at the NY Knicks playoff game in May 2012.
Liam Payne and Niall Horan left the other One Direction guys behind to catch an Orlando Magic vs. New York Knicks game.
Leonardo DiCaprio  treated his then-girlfriend Bar Refaeli  to courtside seats at a Lakers game in April 2010.
Katie Holmes  and Tom Cruise  sat courtside for a Lakers game in March 2010.
Justin Timberlake  sat courtside with Chris Tucker, Chris Kirkpatrick, and then-girlfriend Britney Spears  at the NBA All-Star Game in February 2002.
Lenny Kravitz  and Denzel Washington  chatted with Terrell Owens during a Lakers game in February 2010.
Julianne Moore took in a NY Knicks game with her adorable daughter, Liv Freundlich, in December 2012.
Heidi Klum  and her daughter Leni Samuel watched the Lakers play the New Orleans Hornets in January 2011.
Adrien Brody  and Gerard Butler  chowed down on burgers while watching a Lakers game together in March 2010.
CaCee Cobb and Donald Faison attended a Lakers game at the Staples Center in November 2009.
John Mayer  sat courtside with then-girlfriend Minka Kelly for a NY Knicks game in November 2007.
Justin Bieber  looked happy to sit next to Rihanna  while watching the NBA All-Star Game in February 2011.
Ashton Kutcher  and Mila Kunis  were enthralled in the game between the LA Lakers and New Orleans Pelicans in early March.
Ashton Kutcher  and Kaley Cuoco got excited during a November 2012 Lakers game.
Usher  celebrated as the Cleveland Cavaliers defeated the Orlando Magic during the NBA playoffs in May 2009.
Jeremy Piven  schmoozed with Eva Longoria  and Cameron Diaz  at the NBA All-Star Game in February 2007.
Christina Milian and Christina Aguilera  had a girls' night out at the Lakers game in March 2012.
Jay-Z and Beyoncé Knowles cheered on the Brooklyn Nets as they played the Toronto Raptors in November 2012.
Tobey Maguire  and Leonardo DiCaprio  had a boys' night at an LA Lakers game in December 2009.
Will Smith  shared a laugh with Jay Z, Diddy , and Ashton Kutcher  at a game in February 2004.
Jake Gyllenhaal  and Reese Witherspoon  laughed during a Lakers game in January 2009.
Penélope Cruz and Javier Bardem  celebrated the holidays at the Lakers game together on Christmas Day in 2010.
Mary-Kate Olsen  got cozy with her boyfriend, Olivier Sarkozy, as the two took in a Knicks game in March 2013.
Ryan Phillippe  and David Spencer  cheered on the NY Knicks as they played the Washington Wizards in April.
Charlize Theron  chuckled with friends at an LA Lakers game in April.
Khloé Kardashian cheered on her husband, Lamar Odom, during an LA Clippers game in April.
There was a star-studded cheering section for the NY Knicks in April 2013 — Spike Lee, Jake Gyllenhaal , Christine Taylor, and Ben Stiller  all got together to support the team.
Famous LA Lakers fan Jack Nicholson  was accompanied by his daughter, Lorraine, for the team's April 2013 playoff game against the San Antonio Spurs.
In December 2013, Zac Efron  got involved when his LA Lakers played the Minnesota Timberwolves.