John James Williams (May 17, 1904–January 11, 1988) was an American politician from Delaware who served as a U.S. Senator from 1947 to 1970.

John J. Williams (soldier) (died May 13, 1865) was the last man killed in the American Civil War, at the Battle of Palmito Ranch in Texas.

John Joseph Williams (April 27, 1822–August 30, 1907) was the first Roman Catholic Archbishop of Boston, Massachusetts.