History
German Empire
Name	U-138
Ordered	27 May 1916
Builder	Kaiserliche Werft Danzig
Launched	12 January 1917
Commissioned	26 March 1918
Fate	Unknown
General characteristics [1]
Class and type	Type Large MS submarine
Displacement	1,175 t (1,156 long tons) surfaced 1,534 t (1,510 long tons) submerged
Length	83.50 m (273 ft 11 in) o/a 65.75 m (215 ft 9 in) pressure hull
Beam	7.54 m (24 ft 9 in) o/a 4.85 m (15 ft 11 in) pressure hull
Height	9.46 m (31 ft)
Draught	4.26 m (14 ft)
Installed power	2 × MAN diesel engines, 3,400 bhp (2,500 kW) total 2 × diesel generators for surface dash, 890 brake horsepower (660 kW) total 2 × electric motors, 1,670 shp (1,240 kW) total
Propulsion	2 × propeller shafts
Speed	17 knots (31 km/h; 20 mph) surfaced 9.1 knots (16.9 km/h; 10.5 mph) submerged
Range	10,000 nmi (19,000 km; 12,000 mi) at 8 knots (15 km/h; 9.2 mph) surfaced 50 nmi (93 km; 58 mi) at 4.5 knots (8.3 km/h; 5.2 mph) submerged
Test depth	75 m (246 ft)
Complement	44 men
Armament	6 × torpedo tubes (4 bow, 2 stern) 16 × torpedoes 1 × 15 cm (5.9 in) SK L/45 deck gun with 220 rounds 1 × 8.8 cm (3.5 in) SK L/30 deck gun
Service record
Operations:	None
Victories:	None

SM U-138^{[Note 1]} was one of the 329 submarines serving in the Imperial German Navy in World War I. U-138 was engaged in the naval warfare and took part in the First Battle of the Atlantic. ^[2]

• Gröner, Erich; Jung, Dieter; Maass, Martin (1991). U-boats and Mine Warfare Vessels. German Warships 1815–1945. Vol. 2. Translated by Thomas, Keith; Magowan, Rachel. London: Conway Maritime Press. ISBN 0-85177-593-4.