Clifford Patrick O'Sullivan (December 8, 1897 – October 7, 1975) was a United States circuit judge of the United States Court of Appeals for the Sixth Circuit and previously was a United States district judge of the United States District Court for the Eastern District of Michigan.

[1] O'Sullivan was nominated by President Dwight D. Eisenhower on June 6, 1957, to a seat on the United States District Court for the Eastern District of Michigan vacated by Judge Arthur A. Koscinski.

His service terminated on April 4, 1960, due to his elevation to the Sixth Circuit.

[1] O'Sullivan was nominated by President Eisenhower on January 14, 1960, to a seat on the United States Court of Appeals for the Sixth Circuit vacated by Judge Charles Casper Simons.

His service terminated on October 7, 1975, due to his death.