USS Mobile 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).

The Cleveland-class light cruisers traced their origin to design work done in the late 1930s; at the time, light cruiser displacement was limited to 8,000 long tons (8,100 t) by the Second London Naval Treaty. Following the start of World War II in September 1939, Britain announced it would suspend the treaty for the duration of the conflict, a decision the US Navy quickly followed. Though still neutral, the United States recognized that war was likely and the urgent need for additional ships ruled out an entirely new design, so the Clevelands were a close development of the earlier Brooklyn-class cruisers, the chief difference being the substitution of a two-gun 5 in (127 mm) dual-purpose gun mount for one of the main battery 6 in (152 mm) gun turrets.

Mobile was 610 feet 1 inch (186 m) long overall and had a beam of 66 ft 4 in (20.22 m) and a draft of 24 ft 6 in (7.47 m). Her standard displacement amounted to 11,744 long tons (11,932 t) and increased to 14,131 long tons (14,358 t) at full load. The ship was powered by four General Electric steam turbines, each driving one propeller shaft, using steam provided by four oil-fired Babcock & Wilcox boilers. Rated at 100,000 shaft horsepower (75,000 kW), the turbines were intended to give a top speed of 32.5 knots (60.2 km/h; 37.4 mph). Her crew numbered 1285 officers and enlisted men.

The ship was armed with a main battery of twelve 6 in /47-caliber Mark 16 guns in four 3-gun turrets on the centerline. Two were placed forward in a superfiring pair; the other two turrets were placed aft of the superstructure in another superfiring pair. The secondary battery consisted of twelve 5 in (127 mm) /38-caliber dual-purpose guns mounted in twin turrets. Two of these were placed on the centerline, one directly behind the forward main turrets and the other just forward of the aft turrets. Two more were placed abreast of the conning tower and the other pair on either side of the aft superstructure. Anti-aircraft defense consisted of twenty-eight Bofors 40 mm (1.6 in) guns in four quadruple and six double mounts and twenty-one Oerlikon 20 mm (0.79 in) guns in single mounts.

The ship's belt armor ranged in thickness from 3.5 to 5 in (89 to 127 mm), with the thicker section amidships where it protected the ammunition magazines and propulsion machinery spaces. Her deck armor was 2 in (51 mm) thick. The main battery turrets were protected with 6.5 in (170 mm) faces and 3 in (76 mm) sides and tops, and they were supported by barbettes 6 inches thick. Mobile's conning tower had 5-inch sides.

The keel for Mobile was laid down at the Newport News Shipbuilding and Dry Dock Company on 14 April 1941. She was launched on 15 May 1942, and was commissioned in March 1943. The ship conducted an initial shakedown cruise in Chesapeake Bay and then went on a short training cruise to Casco Bay, Maine. Mobile then departed the East Coast of the United States for the Pacific to join the forces waging the war against Japan. She arrived in Pearl Harbor on 23 July, where she took part in a month of training to prepare for combat operations.

Mobile got underway on 22 August to rendezvous with Task Force 15 the following day. The unit was on the way to raid Marcus Island, which was carried out on 31 August. The ships raided two other Japanese-held islands the following month before joining the rest of the 5th Fleet for the Gilbert and Marshall Islands campaign. This was the first major operation in the island-hopping campaign the US Navy would wage across the Central Pacific, and the fleet's carrier force was primarily occupied with isolating targeted islands, neutralizing Japanese forces on surrounding islands, and supporting ground forces as they made their amphibious assaults. Mobile served as part of the defensive screen for the task force's aircraft carriers while they conducted preparatory raids on Tarawa on 18 September. She was transferred to Task Group 53.3 by 21 October, which sailed west to support landings on Bougainville Island in the Solomon Islands. From there, she sailed for Espiritu Santo, where she was transferred to TG 53.7 for the Battle of Tarawa. Mobile provided gunfire support to the marines fighting on Tarawa and Betio from 20 to 28 November.

Mobile transferred to TF 50 on 1 December, which was the progenitor of the fast carrier task force. Mobile escorted the carriers as they steamed north to launch air strikes on the Marshall Islands, targeting Japanese installations on Kwajalein Atoll and Wotje Atoll. The ships of TF 50 then sailed for Pearl Harbor for replenishment. Mobile was detached to sail on to San Diego, California, where on 29 December she joined the Amphibious Forces, 5th Fleet, serving in Cruiser Division 13 in TG 53.5, part of the escort group for the amphibious assault ships. The ships sortied two weeks later, bound for the Marshalls. Mobile and the rest of her division were detached on 29 January 1944 to bombard Wotje, while the rest of the fleet moved into position to invade Kwajalein. Mobile remained in the area through 6 February, bombarding Japanese forces on the island and assisting in the anti-aircraft defense of the carriers off the islands of Roi and Namur. She thereafter sailed for the fleet's advance base at Majuro, arriving on 12 February to join TF 58 (which is what TF 50 had been re-designated).