Cyrus Nils Tavares (April 12, 1902 – August 3, 1976) was an American lawyer and judge. He served as judge on the United States District Court for the District of Hawaii.
Tavares was born in 1902 in Pukalani, Hawaii. He attended the University of Michigan Law School where he received a J.D. in 1925. He was the first Hawaiian to be inducted into the Order of the Coif. He went into private practice in Maui County, Hawaii, from 1925 to 1927.
Tavares was the deputy attorney general of Hawaii, 1927–1934 before returning to private practice in Honolulu, Hawaii, 1934-1941. During World War II, he was the special deputy attorney general of Hawaii for war matters, 1941–1942, the assistant attorney general of Hawaii, 1942–1943, and the Attorney General of Hawaii, 1944–1947. He returned to private practice from 1947-1960. From March 1953 to September 1956 he served on a Hawaii statehood commission.
Tavares received a recess appointment from U.S. President Dwight D. Eisenhower on October 13, 1960, to a new seat created by 73 Stat. 4 on the United States District Court for the District of Hawaii. He was nominated on January 10, 1961 and confirmed by the United States Senate on September 21, 1961, and received his commission on September 22, 1961. He served as chief judge, 1960–1961 and assumed senior status on April 12, 1972. He died on August 3, 1976.