Seehund (German: "seal"), also known as Type XXVII, was a midget submarine built by Nazi Germany during World War II.

Designed in 1944 and operated by two-man crews, it was used by the Kriegsmarine (German Navy) during the closing months of the war, sinking nine merchant vessels and damaging an additional three, while losing 35 boats, mostly attributed to bad weather.

The origin of the Seehund began with the salvage of the two British X class submarines HMS X6 and X7 which had been lost by the Royal Navy during Operation Source, an attempt to sink the German battleship Tirpitz.

It dispensed with a dual diesel/electric propulsion system, relying instead solely on electrical power in the form of a 12-brake-horsepower (8.9 kW) AEG torpedo motor, on the basis that since it would operate submerged there was no need for a diesel engine.

Since the boat would need to be able to pass through anti-submarine nets and similar obstacles, it was designed without hydroplanes or fins, her trim being controlled with adjustable weights within the pressure hull.

The design was completed at the end of June 1944 and resembled Hecht but had a better boat-shaped external casing for improved seakeeping while surfaced, and saddle tanks.

Seehund had a small sail midships with the air-intake mast, magnetic compass, periscope, and a clear dome which could survive depths of 45 meters (148 ft).

As Admiral Sir Charles Little, Commander-in-Chief, Portsmouth, put it, "Fortunately for us these damn things arrived too late in the war to do any damage".

[citation needed] The last Seehund sorties took place on 28 April and 2 May 1945, when two special missions were performed to resupply the besieged German garrison at Dunkirk with rations.

In April 2002 the wreck of U-5095 was recovered by the Royal Dutch Navy and a civilian salvage team lying buried beneath a beach at Egmond aan Zee in the Netherlands, after having been run aground there by its crew in February 1945, and the remains are now on display at the IJmuiden bunker museum.