Ryan David Leaf (born May 15, 1976) is a former American football player who was a quarterback in the National Football League (NFL) for four seasons. He played for the San Diego Chargers and the Dallas Cowboys between 1998 and 2001, and also spent time with the Tampa Bay Buccaneers and the Seattle Seahawks.

Leaf had a successful college career at Washington State University, where he was a finalist for the Heisman Trophy after his junior year. He was selected as the second overall pick in the 1998 NFL Draft, but his career was short and interrupted by injuries. An episode of NFL Top 10 ranked him as the No. 1 "draft bust" in NFL history.

After having led his high school, Charles M. Russell High School, to the 1992 Montana state title, Leaf played college football at Washington State University. He played in 32 games for the Cougars, starting 24 of them. In his junior year, he averaged 330.6 yards passing per game and threw for a then Pac-10 conference record 33 touchdowns. He also helped the Cougars defeat the Washington Huskies 41-35 for the first time in Husky Stadium since 1985. Leaf ended the school's 67-year Rose Bowl drought and helped bring the Cougars their first Pac-10 championship in school history. Despite a strong early showing by Leaf in the Rose Bowl, the Cougars were defeated 21-16 by the eventual national champion Michigan Wolverines. In 2011, Leaf published a memoir of this season, entitled 596 Switch.^{[citation needed]}