SM U-22 or U-XXII was a U-20-class submarine or U-boat built for and operated by the Austro-Hungarian Navy (German: Kaiserliche und Königliche Kriegsmarine or K.u.K.

The design for U-22 was based on submarines of the Royal Danish Navy's Havmanden class (three of which had been built in Austria-Hungary), and was largely obsolete by the beginning of the war.

The still unfinished U-boat sank in the harbor at Fiume in June but was raised, repaired, and relaunched in October.

After undergoing months of repairs for her failed electric motor in mid 1918, U-22 returned to duty and patrolled off the Montenegrin coast out of Cattaro in August.

When it became apparent to the Austro-Hungarian Navy that the First World War would not be a short one,[1] they moved to bolster their U-boat fleet by seizing the plans for the Danish Havmanden class submarines,[3] three of which had been built at Whitehead & Co. in Fiume.

[3] Due to demands by the Hungarian government,[1] subcontracts for the class were divided between Hungarian and Austrian firms,[4] and this politically expedient solution worsened technical problems with the design, resulting in numerous modifications and delays for the class in general.

Raised from her resting point at a depth of 9 meters (30 ft) the following day, U-22 underwent four months of repairs.

Setting out from Rovigno on 5 January, U-22 unsuccessfully attacked an Italian torpedo boat and two steamships.

Departing the northern Adriatic in late April, U-22 was headed for Cattaro when her electric motor failed.