Geoffrey Edward Blum (born April 26, 1973, in Redwood City, California) is a Major League Baseball (MLB) infielder for the Arizona Diamondbacks. During his major-league career, he has also played for the Montreal Expos, Houston Astros, Tampa Bay Devil Rays, San Diego Padres and Chicago White Sox. As a member of the World Series Champion White Sox in 2005, he hit the game-deciding home run in the longest contest in the history of the Fall Classic.
Before becoming a professional baseball player, he majored in sociology at the University of California, Berkeley and played for the California Golden Bears baseball team.
He began his professional career when he was selected in the seventh round of the 1994 amateur draft by the Montreal Expos. During his time with the Expos, he spent the winter of 1995 in the Australian Baseball League with the Hunter Eagles.