Mark Thomas Teahen (, born September 6, 1981, in Redlands, California) is a Canadian-American Major League Baseball player for the Chicago White Sox. 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. Teahen was one of the featured players in the book Moneyball, which claimed that Teahen had the potential to become the next Jason Giambi.