Ryan Scott Dempster (born May 3, 1977, in Sechelt, British Columbia) is a Major League Baseball starting pitcher for the Chicago Cubs.

Dempster bats and throws right-handed. He had a win-loss record of 76-81, and an ERA of 4.55 in 420 games (195 starts) through the 2008 season.

He was drafted by the Texas Rangers and was traded to the Florida Marlins.He has played for the Florida Marlins (1998-2002), Cincinnati Reds (2002-2003), and Chicago Cubs (2004-present). In August 2003, he underwent Tommy John surgery on his right elbow and made a miraculous recovery from the surgery, taking a little under a year to recover from it, coming back in the last half of 2004 to pitch for the Cubs. In 2005, after starting 6 games, Dempster was named the closer for the Cubs, replacing LaTroy Hawkins.