| 
| History | 
| Nazi Germany | 
| Name | U-636 | 
| Ordered | 20 January 1941 | 
| Builder | Blohm & Voss, Hamburg | 
| Yard number | 612 | 
| Laid down | 2 October 1941 | 
| Launched | 25 June 1942 | 
| Commissioned | 20 August 1942 | 
| Fate | Sunk on 21 April 1945 in the North Atlantic in position 55°50′N 10°31′W / 55.833°N 10.517°W / 55.833; -10.517, by depth charges from HMS Bazely, HMS Drury and HMS Bentinck. | 
| General characteristics | 
| Class & type | Type VIIC submarine | 
| Displacement |  | 
| Length |  | 
| Beam | 
- 6.20 m (20 ft 4 in) o/a
 
- 4.70 m (15 ft 5 in) pressure hull
 
  | 
| Draught | 4.74 m (15 ft 7 in) | 
| Installed power | 
- 2,800–3,200 PS (2,100–2,400 kW; 2,800–3,200 bhp) (diesels)
 
- 750 PS (550 kW; 740 shp) (electric)
 
  | 
| Propulsion |  | 
| Speed | 
- 17.7 knots (32.8 km/h; 20.4 mph) surfaced
 
- 7.6 knots (14.1 km/h; 8.7 mph) submerged
 
  | 
| Range | 
- 8,500 nmi (15,700 km; 9,800 mi) at 10 knots (19 km/h; 12 mph) surfaced
 
- 80 nmi (150 km; 92 mi) at 4 knots (7.4 km/h; 4.6 mph) submerged
 
  | 
| Test depth |  | 
| Complement | 4 officers, 40–56 enlisted | 
| Armament |  | 
| Service record | 
| Part of: | 
 | 
| Identification codes: | 
M 51 601 | 
| Commanders: | 
- Kptlt. Hans Hildebrandt
 
- 20 August 1942 – 14 February 1944
 
- Oblt.z.S. Eberhard Schendel
 
- 15 February 1944 – 21 April 1945
 
  | 
| Operations: | 
- 15 patrols:
 
- 1st patrol:
 
- a. 2 May – 8 June 1943
 
- b. 24 – 27 July 1943
 
- c. 28 – 31 July 1943
 
- 2nd patrol:
 
- a. 31 July – 7 August 1943
 
- b. 14 – 16 August 1943
 
- 3rd patrol:
 
- a. 17 – 30 August 1943
 
- b. 5 – 9 September 1943
 
- c. 24 – 25 October 1943
 
- d. 27 – 31 October 1943
 
- e. 2 – 3 November 1943
 
- 4th patrol:
 
- a. 6 – 17 November 1943
 
- b. 18 – 19 November 1943
 
- c. 21 – 22 November 1943
 
- 5th patrol:
 
- 23 November – 27 December 1943
 
- 6th patrol:
 
- 30 December 1943 – 8 January 1944
 
- 7th patrol:
 
- a. 26 January – 2 February 1944
 
- b. 4 – 5 February 1944
 
- c. 8 – 11 February 1944
 
- d. 31 March – 2 April 1944
 
- 8th patrol:
 
- a. 8 April – 3 May 1944
 
- b. 5 – 7 May 1944
 
- c. 23 – 24 June 1944
 
- 9th patrol:
 
- a. 27 June – 23 July 1944
 
- b. 24 July 1944
 
- 10th patrol:
 
- a. 25 August – 12 September 1944
 
- b. 16 – 18 September 1944
 
- 11th patrol:
 
- 25 September – 3 October 1944
 
- 12th patrol:
 
- a. 6 October – 12 November 1944
 
- b. 14 – 16 November 1944
 
- 13th patrol:
 
- 4 – 16 December 1944
 
- 14th patrol:
 
- a. 25 December 1944 – 30 January 1945
 
- b. 1 – 3 February 1945
 
- 15th patrol:
 
- 1 – 21 April 1945
 
  | 
| Victories: | 
1 merchant ship sunk  (7,169 GRT) | 
German submarine U-636 was a Type VIIC U-boat built for Nazi Germany's Kriegsmarine for service during World War II.
She was laid down on 2 October 1941 by Blohm & Voss, Hamburg as yard number 612, launched on 25 June 1942 and commissioned on 20 August 1942 under Oberleutnant zur See Hans Hildebrandt.