'Ursula' (i) was the German programme of U-boat operations in support of General Francisco Franco y Bahamonde’s nationalist insurgent forces in the Spanish Civil War (1936/39).

Though the programme yielded little in the way of tangible results, it was nonetheless invaluable in providing the fledgling U-boat arm with operational and technical experience.

The undertaking involved two U-boats in active operations around the waters near Spain against the ships of the Spanish republican navy under the overall command of Konteradmiral (from 1 April 1937 Vizeadmiral) Hermann Boehm in Berlin. The operation started on 20 November 1936 with the secret movement of U-33 and U-34 from Wilhelmshaven with all identification marks obscured. The U-boats entered the Mediterranean on the night of 27/28 November, and took over from Italian submarines. The boats were under orders that if they were damaged they were to sail to the Italian port of La Maddelena on the island of Sardinia, and enter under an Italian ensign.

U-33 operated around Alicante, and U-34 around Cartagena, and the captains of both boats found that difficulties in identifying legitimate targets and concerns about discovery limited their operations. Moreover, the torpedoes they used were also disastrously prone to malfunctions. During their return to Wilhelmshaven in December, the Spanish republican submarine C-3 was sunk: the Germans claimed this resulted from the detonation of a torpedo fired by U-34, although the Spanish republican enquiry claimed its loss was the result of an internal explosion.

The return of the two boats marked the official end of 'Ursula'. It seems, though, that other U-boats were despatched to Spanish waters in mid-1937, but all details are obscure. The boats involved are believed to have been U-25, U-26, U-27, U-28, U-31 and U-35.