Mark Thomas Teahen (born September 6, 1981) is an American-Canadian former professional baseball infielder who played in Major League Baseball (MLB) for the Kansas City Royals, Chicago White Sox, and Toronto Blue Jays. He graduated from Yucaipa High School in 1999 and attended St. Mary's College in California. Teahen was drafted 39th overall in the 2002 draft by the Oakland Athletics with a sandwich pick between the first and second rounds. He was featured in the book Moneyball, which noted the Athletics considered that Teahen could have the potential to become the next Jason Giambi.