SMS Schleswig-Holstein (pronounced [ˌʃleːsvɪç ˈhɔlʃtaɪn] ^ⓘ) was the last of the five pre-dreadnought Deutschland-class battleships built by the German Kaiserliche Marine. The ship, named for the province of Schleswig-Holstein, was laid down in the Germaniawerft dockyard in Kiel in August 1905 and commissioned into the fleet nearly three years later. The ships of her class were already outdated by the time they entered service, being inferior in size, armor, firepower and speed to the new generation of dreadnought battleships.

Schleswig-Holstein fought in both World Wars. During World War I, she saw front-line service in II Battle Squadron of the High Seas Fleet, culminating in the Battle of Jutland on 31 May – 1 June 1916. Schleswig-Holstein saw action during the engagement, and was hit by one large-caliber shell. After the battle, Schleswig-Holstein was relegated to guard duty in the mouth of the Elbe River before being decommissioned in late 1917. As one of the few battleships permitted for Germany by the terms of the Treaty of Versailles, Schleswig-Holstein was again pressed into fleet service in the 1920s. In 1935, the old battleship was converted into a training ship for naval cadets.

Schleswig-Holstein fired the first cannon shots of World War II when she bombarded the Polish base at Danzig's Westerplatte in the early morning hours of 1 September 1939. The ship was used as a training vessel for the majority of the war, and was sunk by British bombers in Gotenhafen in December 1944. Schleswig-Holstein was subsequently salvaged and then beached for use by the Soviet Navy as a target. As of 1990, the ship's bell was on display in the Bundeswehr Military History Museum in Dresden.

The passage of the Second Naval Law in 1900 under the direction of Vizeadmiral (VAdm—Vice Admiral) Alfred von Tirpitz secured funding for the construction of twenty new battleships over the next seventeen years. The first group, the five Braunschweig-class battleships, were laid down in the early 1900s, and shortly thereafter design work began on a follow-on design, which became the Deutschland class. The Deutschland-class ships were broadly similar to the Braunschweigs, featuring incremental improvements in armor protection. They also abandoned the gun turrets for the secondary battery guns, moving them back to traditional casemates to save weight. The British battleship HMS Dreadnought—armed with ten 12-inch (30.5 cm) guns—was commissioned in December 1906. Dreadnought's revolutionary design rendered every capital ship of the German navy obsolete, including the Deutschland class.

Schleswig-Holstein had a length of 127.60 m (418 ft 8 in), a beam of 22.20 m (72 ft 10 in), and a draft of 8.21 m (26 ft 11 in). She displaced 13,200 metric tons (13,000 long tons) normally and up to 14,218 metric tons (13,993 long tons) at combat loading. She was equipped with three triple expansion engines and twelve coal-fired water-tube boilers that produced a rated 16,767 indicated horsepower (12,503 kW) and a top speed of 19.1 knots (35.4 km/h; 22.0 mph). In addition to being the second-fastest ship of her class, Schleswig-Holstein was the second-most fuel efficient. At a cruising speed of 10 knots (19 km/h; 12 mph), she could steam for 5,720 nautical miles (10,590 km; 6,580 mi). She had a standard crew of 35 officers and 708 enlisted men.

The ship's primary armament consisted of four 28 cm SK L/40 guns in two twin turrets; one turret was placed forward and the other aft. Her offensive armament was rounded out with a secondary battery of fourteen 17 cm (6.7 in) SK L/40 guns mounted individually in casemates. A battery of twenty-two 8.8 cm (3.5 in) SK L/45 guns in single mounts provided defense against torpedo boats. The ship was also armed with six 45 cm (17.7 in) torpedo tubes, all below the waterline. One was in the bow, one in the stern, and four on the broadside. Her armored belt was 240 mm (9.4 in) thick amidships in the citadel, and she had a 40 mm (1.6 in) thick armored deck. The main battery turrets had 280 mm (11 in) thick sides.

Schleswig-Holstein was laid down on 18 August 1905 at the Germaniawerft dockyard in Kiel, under the provisional name "Q". She was launched on 17 December 1906, the last pre-dreadnought battleship of the German navy. At Schleswig-Holstein's launching ceremony, she was christened by Augusta Victoria of Schleswig-Holstein, the German Empress; Wilhelm II was also in attendance. Ernst Gunther, the Duke of Schleswig-Holstein, gave the commissioning speech.

Upon completion, Schleswig-Holstein was commissioned for sea trials on 6 July 1908. Her crew largely came from her sister ship Schlesien. On 21 September the ship was assigned to II Battle Squadron of the High Seas Fleet, alongside her sister ships. In November, fleet and unit exercises were conducted in the Baltic Sea. The training regimen in which Schleswig-Holstein participated followed a similar pattern over the next five years. Fleet maneuvers were conducted in the spring, followed by a summer cruise to Norway, and additional fleet training in the fall. This included another cruise into the Atlantic, from 7 July to 1 August 1909.