SM U-84 was one of the 329 submarines serving in the Imperial German Navy (Kaiserliche Marine) in World War I. U-84 was engaged in the naval warfare and took part in the First Battle of the Atlantic.

The submarine was powered by two 2,400 metric horsepower (1,800 kW; 2,400 shp) engines for use while surfaced, and two 1,200 metric horsepower (880 kW; 1,200 shp) engines for use while submerged.

[2] When submerged, she could operate for 56 nautical miles (104 km; 64 mi) at 5 knots (9.3 km/h; 5.8 mph); when surfaced, she could travel 11,220 nautical miles (20,780 km; 12,910 mi) at 8 knots (15 km/h; 9.2 mph).

U-84 was fitted with four 50 centimetres (20 in) torpedo tubes (two at the bow and two at the stern), twelve to sixteen torpedoes, and one 10.5 cm (4.1 in) SK L/45 deck gun.

She had a complement of thirty-five (thirty-one crew members and four officers).