Oliver Deveta Hamlin, Jr. (November 30, 1892 – December 28, 1973) was a United States federal judge.
Born in Oakland, California, Hamlin received a B.L. from the University of California in 1914. He was a Deputy district attorney of Alameda County, California from 1915 to 1920, and was in private practice in Oakland from 1920 to 1947. He was a judge on the Superior Court, Alameda County, California from 1947 to 1953.
On July 23, 1953, Hamlin was nominated by President Dwight D. Eisenhower to a seat on the United States District Court for the Northern District of California vacated by Monroe Mark Friedman. Hamlin was confirmed by the United States Senate on August 1, 1953, and received his commission on August 3, 1953.
On March 6, 1958, Eisenhower nominated Hamlin for elevation to a seat on the United States Court of Appeals for the Ninth Circuit vacated by William Denman. Hamlin was again confirmed by the Senate on March 25, 1958, and received his commission the following day. He assumed senior status on September 5, 1963, serving in that capacity until his death.