Marcus Thomas Morris Sr. (born September 2, 1989) is an American former professional basketball player. He played college basketball for the Kansas Jayhawks before being selected 14th overall by the Houston Rockets in the 2011 NBA draft.

Morris was born in Philadelphia, Pennsylvania, to Thomasine "Angel" Morris. He has four brothers, Donte, Blake, David and twin Markieff, who also plays in the NBA.

Considered a four-star recruit by Rivals.com, Morris was listed as the No. 10 power forward and the No. 29 player in the nation in 2008.

Morris attended the University of Kansas, where he majored in American studies. Morris was named the 2010–11 Big 12 Conference Men's Basketball Player of the Year. He also was named a second team All-American for his play in the 2010–11 basketball season by both the Associated Press and the National Association of Basketball Coaches, and a third team All-America by Fox Sports. On March 30, 2011, Morris was named to the ten-member John R. Wooden Award Men's All American team. Morris and his brother signed with a sports agent from Los Angeles, and announced that they would enter the 2011 NBA draft.

Morris was selected by the Houston Rockets with the 14th overall pick in the 2011 NBA draft, five minutes after his brother Markieff was taken with the 13th pick by the Phoenix Suns. Morris was assigned to the Rio Grande Valley Vipers of the NBA Development League on January 2, 2012. In his first game in the D-League on January 6, 2012, he recorded 33 points and 16 rebounds in a narrow 105–103 loss to the Dakota Wizards. Morris returned to the Rockets on January 16, was reassigned to the Rio Grande Valley Vipers on February 3, and returned to the Rockets again on February 20.

After an injury to Patrick Patterson, Rockets head coach Kevin McHale named Morris the opening day starter at power forward for the 2012–13 season. When told he would be starting, Morris thought McHale was kidding, since he rarely played his rookie season and was hurt during the preseason. During the course of the season, Morris was the backup power forward to Patterson, and started 17 games while Patterson was injured. His three-point shot was much improved from his rookie season, more than tripling the percentage from 12% to 38%.

On February 21, 2013, Morris was traded to the Phoenix Suns, reuniting him with his brother Markieff. The next day, Morris played his first game with his brother in the last six minutes of a loss to the Boston Celtics, as he recorded seven points, two steals, and a rebound, despite having no formal training from the Suns before entering the game. This marked the second time that twin brothers played for the same NBA team; Dick and Tom Van Arsdale also played together for the Suns during the 1976–77 season. On March 1, 2013, Morris scored 16 points to help the Suns defeat the Atlanta Hawks 92–87. He made four out of five three-point attempts. Morris went on to start alongside Markieff on March 9, 2013, against his former team, the Rockets, which made the Morris twins the first set of twins to ever start for the same NBA team.

On September 29, 2014, Morris signed a multi-year contract extension with the Suns. In the Suns' 2014–15 season opener on October 29, 2014, he recorded 21 points in the 119–99 win over the Los Angeles Lakers. On January 7 game against the Minnesota Timberwolves, Morris received a technical foul and was caught on national TV berating head coach Jeff Hornacek about the situation. It resulted in Morris not playing for the rest of the game. His other antics during his final season with the Suns and afterwards, though, led to AZCentral.com labeling him one of Arizona's biggest sports villains.