Pat Mehaffy (October 8, 1904 – January 31, 1981) was a United States federal judge.
Born in Little Rock, Arkansas, Mehaffy received an LL.B. from the University of Arkansas School of Law in 1927. He was in private practice in Little Rock, Arkansas from 1929 to 1930. He was an Assistant state attorney general of Arkansas from 1929 to 1933. He was a Chief deputy prosecuting attorney of Pulaski County, Arkansas from 1934 to 1938. He was a Prosecuting attorney of Pulaski County, Arkansas from 1939 to 1940. He was in private practice in Little Rock, Arkansas from 1940 to 1963.
Mehaffy was a federal judge on the United States Court of Appeals for the Eighth Circuit. Mehaffy was nominated by President John F. Kennedy on June 24, 1963, to a seat vacated by Joseph William Woodrough. He was confirmed by the United States Senate on July 15, 1963, and received his commission on July 16, 1963. He served as chief judge from 1973-1974. He assumed senior status on August 31, 1974. Mehaffy served in that capacity until his death, in Little Rock, Arkansas.