HMS Avon, later renamed NRP Nuno Tristão, was a River-class frigate of the Royal Navy (RN). Avon was built to the RN's specifications as a Group II River-class frigate. She served in the North Atlantic during World War II. After her commission, Avon was deployed in the Indian Ocean, where she rescued the survivors of the sunken Norwegian freighter Tarifa. In 1945, she took part in the Battle of Okinawa, where she came under air attack. Postwar, Avon was paid off and placed in the Reserve Fleet, where she stayed until 1949. That year, she was sold to Portugal and renamed NRP Nuno Tristão.