CSS Fredericksburg was a casemate ironclad that served as part of the James River Squadron of the Confederate States Navy during the American Civil War. Laid down in 1862 and launched the following year, she did not see action until 1864 due to delays in receiving her armor and guns. After passing through the obstructions at Drewry's Bluff in May 1864, she participated in several minor actions on the James River and fought in the Battle of Chaffin's Farm from September 29 to October 1. On January 23 and 24, 1865, she was part of the Confederate fleet at the Battle of Trent's Reach, and was one of only two Confederate ships to make it past the obstructions at Trent's Reach. After the Confederate attack failed, Fredericksburg withdrew with the rest of the James River Squadron. On April 3, as the Confederates were abandoning Richmond, Fredericksburg and the other vessels of the James River Squadron were burned. Her wreck was located in the 1980s, buried under sediment.

In mid-1862, Fredericksburg was laid down by the Confederate States Navy in the Rocketts Landing area of Richmond, Virginia to a plan by the Chief Naval Constructor, John L. Porter. The ship was one of the ironclads built to Porter's shallow-draft "diamond hull" configuration with a flat bottom and hull sides that met the base of the casemate at a 90° angle. By substituting straight lines and angles for the traditional keel and curving frame of the hull, Porter optimized his design to be quickly built by ordinary carpenters, rather than highly skilled shipwrights that were in short supply in the Confederacy, at the cost of being able to mount fewer guns than those ironclads built with traditional hulls. Their shallow draft and flat bottom restricted these ships to rivers and inland waters.

Porter supervised the work of constructing Fredericksburg, but it is uncertain how exactly he followed his design as surviving documents disagree in many ways. The plan showed an overall length of 188 feet (57.3 m) and a length between perpendiculars of 170 feet (51.8 m) with a maximum beam of 40 feet 3 inches (12.3 m), a moulded beam of 34 feet (10.4 m) and a depth of hold of 9 ft (2.7 m). The naval historian Saxon T. Bisbee quotes a beam of 40 feet (12.2 m) with a depth of hold of 10 feet 10 inches (3.30 m) and a draft of 9 to 10 feet (2.7 to 3.0 m) while US Navy historian Paul J. Marcello provides a figure of 13 feet 6 inches (4.11 m) for the ironclad's draft. She had a tonnage of 700 long tons. The ship's casemate was shaped like a rectangle and Porter's plan showed two pilothouses on the casemate's roof, although operational reports from her captain make no mention of the rear pilothouse.

The Tredegar Iron Works in Richmond was contracted to produce her propulsion system, although Bisbee believes that it is possible that the Richmond-based Shockoe Foundry may have produced them. The ship was propelled by a pair of 24-inch-diameter (61 cm) direct-acting steam engines that each drove a 7-foot (2.1 m) propeller. Porter's plan shows Fredericksburg as having three horizontal boilers measuring 7 feet tall, 5 feet (1.5 m) in diameter, and 15 feet (4.6 m) long, but it is not known if the final construction varied from the blueprints or not. Bisbee believes that the boilers probably were of the fire-tube type. Fredericksburg could move at a speed of about 5 knots (9.3 km/h; 5.8 mph) and had a crew of 150. She also carried about 20 to 25 Confederate States Marines in case of a battle that required naval boarding.

Fredericksburg eventually received her armament of one 7-inch (178 mm) Brooke rifle on a pivot mount in the bow, two 6.4-inch (163 mm) Brooke rifles, one on each broadside and a 10-inch (25.4 cm) Columbiad muzzle-loading smoothbore gun on a pivot mounting in the stern. Naval historian Paul H. Silverstone states that she was armed with one 11-inch (27.9 cm) smoothbore cannon, an 8-inch (20.3 cm) rifled cannon, and two 6.4-inch (16.3 cm) rifled cannons, and naval historian W. Craig Gaines states that she was armed with four 6-inch (15.2 cm) rifled cannons.

Gaines states that she had 4 inches (10.2 cm) of wrought-iron armor. The area where the casemate met the deck was armored with 2 inches (5.1 cm) of iron, and the armor extended below the waterline. The top of the casemate consisted of 2-inch-thick iron bars, spaced 9 inches (23 cm) apart. After the Battle of Chaffin's Farm in September–October 1864, the ship's captain recommended that additional iron bars be positioned between the bars to better protect the crew, although it is uncertain if this was ever done. Fredericksburg had less armor than Virginia II, which gave her a lighter draft but made her comparatively weaker.

Named for the Virginia city, Fredericksburg's construction was partially funded from monies raised by women's organizations for ship construction; the ship was one of several ironclads sometimes known as the "Ladies Gunboats". An attempt to launch the warship on June 6, 1863, failed when the Confederates were unable to get her into the water, but another on June 11 was successful. Her fitting out was prolonged by a lack of iron, which was in short supply in the Confederacy. The shortage led to work on the ironclad CSS Virginia II being delayed until after Fredericksburg was armored, as there was not enough metal available to work on both ships at the same time. The ship was complete, except for her armament by November 30. High waters on the James River in early 1864 threatened to wash away stockpiles of timber and inundate the shipyard's wharves, further delaying her completion.

In March, Fredericksburg was commissioned and taken to Drewry's Bluff on the James River, where she was fitted out, placed under the command of Commander Thomas R. Rootes. She was assigned to the James River Squadron. The James River Squadron had been commanded by Captain French Forrest until May 6, when Captain John K. Mitchell replaced Forrest. As of April 30, Fredericksburg's armament was reported to be close, but not quite, complete, and she was still not fully ready when Mitchell took command. By May 15, she was fully ready for combat.