The oldest active player in Major League Baseball, as of Sept. 2014, is Jason Giambi. He is 43 years old and plays for the Cleveland Indians.
The oldest player to ever play in an MLB game was Satchel Paige, as of 2014. He was 59 years old when he played a game for the Kansas City Royals in 1965. The oldest player to play in the postseason was Jack Quinn of the Philadelphia Athletics, who played in the 1929 World Series at 46 years old. In 2012, Jamie Moyer became the oldest pitcher in MLB history to record a win. He was 49 years old.