Dennis Joseph O'Toole is an American former professional baseball player. A right-handed relief pitcher and the younger brother of 1963 National League All-Star lefthander Jim O'Toole, Dennis appeared in 15 Major League games spread over five seasons (1969–1973) for the Chicago White Sox. He stood 6 feet 3 inches (1.91 m) tall and weighed 195 pounds (88 kg).