HMS Spur was a S-class submarine of the third batch built for the Royal Navy during World War II.

[2] For surface running, the boats were powered by two 950-brake-horsepower (708 kW) diesel engines, each driving one propeller shaft.

[1] On the surface, the third batch boats had a range of 7,500 nautical miles (13,900 km; 8,600 mi) at 10 knots (19 km/h; 12 mph) and 120 nmi (220 km; 140 mi) at 3 knots (5.6 km/h; 3.5 mph) submerged.

During her wartime career, Spur claimed to have sunk a total of eleven junks in the Strait of Malacca, during her service in the Far East.

[4] The boat survived the Second World War and was sold to the Portuguese navy in November 1948, where she was renamed NRP Narval.