John B. Callahan (born September 20, 1969) was the 10th Mayor of Bethlehem, Pennsylvania. He was the Democratic nominee in an unsuccessful 2010 bid for United States Representative for Pennsylvania's 15th congressional district. Callahan was inaugurated Mayor of Bethlehem in 2004 at the age of 34-years old, becoming the second youngest mayor in the city's history after former Mayor Don Cunningham, who was 31.