Casey Austin Keenum (born February 17, 1988) is an American professional football quarterback for the Chicago Bears of the National Football League (NFL). He played college football for the Houston Cougars, where he became the NCAA's all-time leader in total passing yards, touchdowns, and completions. In the 2008 college football season, Keenum ranked first nationally in total offense and second in total passing yards.

During the 2011 season, Keenum became the Football Bowl Subdivision's all-time leader in total offense, as well as the all-time leader in total passing yards and touchdown passes by a college quarterback. As a result of his on-field contributions to Houston's success, Keenum was named to several All-American lists. He is the only quarterback in Division I FBS football history to have passed for more than 5,000 yards in each of three seasons, and the only college player to reach the 20,000-yards plateau in career total offense.

After being signed by the Houston Texans as an undrafted free agent in 2012, Keenum threw for 1,760 yards and nine touchdowns in the eight games he started for the Texans in 2013 before being waived prior to the 2014 season. He was then signed to the St. Louis Rams' practice squad and then re-signed with the Texans later in 2014. In 2015, the Rams (who later relocated to Los Angeles) traded a draft pick to the Texans for Keenum, where he played until signing as a free agent with the Minnesota Vikings in 2017.

After starter Sam Bradford was injured, Keenum came in and had a career year, setting highs in starts, passing yards, completions, and touchdowns. He led the Vikings to a 13-win regular season, followed by a last-second win, known as the Minneapolis Miracle, over the New Orleans Saints in the playoffs. Following that, Keenum played for the Denver Broncos, Washington Redskins, Cleveland Browns, Buffalo Bills, and Texans. He is known for being a journeyman quarterback by having played for eight different NFL teams across seven divisions.

Keenum played football for Wylie High School in Abilene, Texas. During his high school football career, Keenum passed for 6,783 yards and 48 touchdowns and rushed for 41 touchdowns and 2,000 yards for the Bulldogs. Logging 42 starts at quarterback, he posted a career record of 31–11. In 2004, Keenum led Wylie in the game-winning drive for a 17–14 victory over Cuero High School of Cuero, Texas in the Texas Class 3A Division I Championship. Keenum earned varsity letters in basketball and track during his high school career.

In addition to being recruited by the University of Houston, Keenum received walk-on offers from Baylor, Missouri, North Texas, and UTEP, but Houston was the only FBS university to offer him a scholarship over FCS offers from Sam Houston State and Stephen F. Austin.

Keenum began his college career for the Houston Cougars during the 2006 season. During Keenum's freshman season, senior Kevin Kolb held the starting quarterback position for the Cougars, leading the coaching staff to redshirt Keenum for the season. The 2006 Cougars won the Conference USA championship, and Kolb was drafted by the NFL's Philadelphia Eagles.

In fall camp before the 2007 season, the Cougars held a de facto quarterback competition to fill the starting spot vacated by the departure of four-year starter Kevin Kolb. The competition swung between Keenum and sophomore Blake Joseph throughout two-a-days and during much of the season, with each player displaying a different set of strengths and weaknesses.