German submarine U-573 was a Type VIIC U-boat built for Nazi Germany's Kriegsmarine for service during World War II.

The submarine was powered by two Germaniawerft F46 four-stroke, six-cylinder supercharged diesel engines producing a total of 2,800 to 3,200 metric horsepower (2,060 to 2,350 kW; 2,760 to 3,160 shp) for use while surfaced, two Brown, Boveri & Cie GG UB 720/8 double-acting electric motors producing a total of 750 metric horsepower (550 kW; 740 shp) for use while submerged.

U-573's second patrol involved the boat slipping past the heavily defended Strait of Gibraltar into the Mediterranean,[6] where she sank the Norwegian Hellen (5,289 GRT) with two torpedoes on 21 December 1941.

The Spanish authorities granted U-573 a three-month period for repairs, which prompted several strong protests from the British Embassy in Madrid.

On 19 May Heinsohn flew from Madrid to Stuttgart, then travelled on to Berlin, in order to discuss the situation with the Kriegsmarine.

Realizing that even three months would not be enough to repair the boat, the Kriegsmarine sold the vessel to Spain for 1.5 million ℛ︁ℳ︁.

On 2 August 1942, at 10 am, (one day before the three-month period was due to expire), the Spanish navy commissioned the boat as the G-7.

The damage caused by the British attack was found to be more extensive than was first thought; also German technical assistance and parts were difficult to obtain in the last years of World War II and after.

Despite the Type VII being out-dated by the end of World War II, G-7 was the most modern of Spain's submarine fleet; her other vessels (two ex-Italian, and four home-built boats) dating from the early 1930s.

In 1958 Arca-Filmproduktion GmbH rented G-7 to take part in the semi-fictitious movie U 47 – Kapitänleutnant Prien, partially based on his patrol to Scapa Flow, where he sank HMS Royal Oak.