John Thomas Flavin (born May 7, 1942) is an American former professional baseball pitcher who appeared in five games in the major leagues for the Chicago Cubs in 1964.

Born in Albany, California, Flavin threw and batted left-handed, stood 6 feet 2 inches (1.88 m) tall and weighed 208 pounds (94 kg).

After he spent four years in their farm system — including a 12–2 season for Triple-A San Diego in 1962 — Cincinnati sold Flavin's contract to the Cubs in April 1964.

Flavin won seven of 12 decisions at Triple-A Salt Lake City, then was recalled to Chicago in August.

In 42⁄3 total innings in the majors, he allowed 11 hits, three bases on balls, and seven earned runs; he struck out five.