Jason Scott Marquis (pronounced /mɑrˈkiː/) (born August 21, 1978, in Manhasset, New York) is an American Major League Baseball All Star starting pitcher for the Colorado Rockies. He previously pitched for the Atlanta Braves, St. Louis Cardinals, and Chicago Cubs.

As a 12-year-old, Marquis pitched his Little League team to third place in the Little League World Series with a no-hitter. He is one of only a few ballplayers to have played in both a Little League World Series and a Major League World Series. Later, he pitched his high school team to consecutive New York City championships. Marquis was drafted in the first round out of high school by the world champion Atlanta Braves, and reached the majors as a 21-year-old in 2000.

As a major leaguer, Marquis has won 11 or more games for six straight years through 2009, and started 28 or more games in each of the years 2004–08. His 65 wins from 2004–08 season ranked 7th among N.L. pitchers. Through 2008, in games that were late and close Marquis held batters to a .215 batting average. He has also excelled with the bat, winning the Silver Slugger Award in 2005.