John Joseph "Jack" Hannahan IV (born March 4, 1980, in St. Paul, Minnesota) is an American professional baseball third baseman with the Cleveland Indians of Major League Baseball. Mainly a third baseman, Hannahan has also played other infield positions.
He attended The University of Minnesota where he was named All-American. As a freshman, he hit .360 with 28 runs, 9 doubles, 4 home runs and 30 RBI's in 1999.
In 2000 he batted .327 with 46 runs, 18 doubles, 4 triples, 8 home runs, 43 RBI's and 9 stolen bases during his sophomore season. He was named Big Ten Player of the Year and First-Team All-Big Tenuring his junior season after hitting .372 with 65 runs, 20 doubles, 4 triples, 15 home runs, 63 RBI's and 16 stolen bases. He led the Big Ten Conference in runs, home runs and RBI's. Hannahan played for a summer collegiate team in the Northwoods League called the Mankato Mashers, now known as the Moondogs.