USS Portsmouth was a Cleveland-class light cruiser of the United States Navy, which were built during World War II. The class was designed as a development of the earlier Brooklyn-class cruisers, the size of which had been limited by the First London Naval Treaty. The start of the war led to the dissolution of the treaty system, but the dramatic need for new vessels precluded a new design, so the Clevelands used the same hull as their predecessors, but were significantly heavier. The Clevelands carried a main battery of twelve 6-inch (152 mm) guns in four three-gun turrets, along with a secondary armament of twelve 5 in (127 mm) dual-purpose guns. They had a top speed of 32.5 knots (60.2 km/h; 37.4 mph). Portsmouth was laid down in 1943, launched in September 1944, and commissioned in June 1945. By the time she completed her initial sea trials, the war had ended, so her career was short and uneventful. She made three overseas cruises to visit ports in Africa and the Mediterranean Sea between 1946 and 1948 before conducting training cruises later in 1948. The following year, she was decommissioned and assigned to the Atlantic Reserve Fleet, where she remained until 1970, when she was broken up.