Dan Duffy (born March 11, 1966) is a Republican member of the Illinois Senate. He represents the 26th Senate District which includes Barrington, Barrington Hills, North Barrington, Libertyville, Mundelein, Lake Zurich, Fox River Grove, Lakewood Hills, Cary, Hawthorn Woods, Lake in the Hills, Cuba and Kildeer.On September 10, 2015, Duffy announced he would not be running for a third term. He resigned after his endorsed successor won the Republican primary.