The H class was a series of battleship designs for Nazi Germany's Kriegsmarine, which were intended to fulfill the requirements of Plan Z in the late 1930s and early 1940s.

The first variation, "H-39", called for six ships to be built, essentially as enlarged Bismarck-class battleships with 40.6 cm (16 in) guns and diesel propulsion.

The Construction Office of the Oberkommando der Marine (OKM) concluded their work with the "H-41" design, and were not involved in subsequent plans.

What work that had been accomplished was halted; the assembled steel remained on the slipway until November 1941, when the OKM ordered it be sent for scrap and used for other purposes.

[a] The Oberkommando der Marine (OKM) issued staff requirements at the end of October for a ship of 35,000 long tons (36,000 t) armed with eight 38 cm guns with a speed of 30 knots (56 km/h; 35 mph).

[4] Admiral Werner Fuchs, responsible for the staff section in the OKM that determined the operating requirements for the ship, discussed the vessel's design with Adolf Hitler, the leader of Germany.

He approved the plan on 18 January and granted the Kriegsmarine unlimited power to bring the construction program to fruition.

[7] The keels for the first two ships were laid at the Blohm & Voss dockyard in Hamburg and the Deschimag shipyard in Bremen on 15 July and 1 September 1939, respectively.

The hull contained twenty-one large watertight compartments and a double bottom that extended for 89 percent of the length of the keel.

[2] The power-plant was rated at 165,000 shaft horsepower (123,000 kW) and 256 rpm; it provided a top speed of 30 knots (56 km/h; 35 mph) as designed.

[18] Unlike those mounted on the Scharnhorst and Bismarck classes, these guns were armored to protect their crews from shrapnel, debris, and strafing attacks.

Historians William Dulin and Robert Garzke note that the anti-aircraft battery as designed was too weak to effectively defend against the high-performance aircraft that came into service in the late 1930s and 1940s, and speculate that "it would have been augmented before the ships were completed.

"[20] The design team envisioned the H-class ships fighting at relatively close range, and therefore selected the armor system that had been used by German battleship constructors since the Nassau class of 1907.

[20] The side belt, which consisted of Krupp cemented steel armor (KCA), was 300 mm (11.8 in) thick in the central section that covered the ammunition magazines and machinery spaces.

[22] A 45 mm (1.8 in) thick torpedo bulkhead composed of Wotan Weich steel backed the side armor and provided defense against underwater weapons.

[22] Two armored decks composed of Wotan Hart steel protected the ships from plunging fire and aerial weapons.

[24] Concerned with the fate of the battlecruiser Lützow at the Battle of Jutland,[e] the designers opted to provide relatively heavy bow armor for the H-class ships.

[27] In early July 1940, Hitler ordered the navy to examine new battleship designs and how wartime experience might be incorporated.

A study was completed on 15 July, and contained several recommendations for the H-class ships, including increasing the freeboard and strengthening the horizontal protection.

[31] Bomb damage sustained by Scharnhorst in July 1941 provided the impetus for the effort to increase the horizontal protection for the H-class.

The initial redesign called for an increase of only 5,000 long tons (5,100 t), 40 percent of which was additional deck armor, the remainder being used for a larger-caliber main battery.

The design staff determined that modifications to the ammunition hoists and loading equipment would be easily effected and that the original turrets could be retained.

[8] Wartime experience with the Scharnhorst class indicated that the torpedo-defense system was insufficiently strong to protect the H-39 design from underwater damage.

[8] The loss of Bismarck in May 1941 also influenced the design; two large skegs were added to the outboard shafts to protect them and increase support for the stern while in drydock.

These changes resulted in full load displacement increasing to 77,752 long tons (79,000 t) and maximum speed further decreasing to 28 kn (52 km/h; 32 mph).

[35] As detailed design continued into 1942, the OKM planned to begin construction six to nine months after demobilization, initially at Blohm & Voss and the Deutsche Werke shipyard in Kiel.

Speer reassigned some members of the H class design staff to work on new U-boats and other tasks deemed critical to the war effort.

[37] The Schiffsneubaukommission (New Ships Construction Commission),[36] intended to liaise with Speer and the OKM, was created and placed under the direction of Admiral Karl Topp.

[37] The results were purely study projects intended to determine the size of a ship with strong enough armor to counter the rapidly increasing power of bombs deployed by the Allies during the war.

The Construction Office of the OKM sought to disassociate itself from the projects, which they found to be of doubtful merit and unnecessary for German victory.