SM U-6 was one of the 329 submarines serving in the Imperial German Navy in World War I. U-6 was engaged in naval warfare and took part in the First Battle of the Atlantic. Torpedoed by HMS E16 off Stavanger, Norway on 15 September 1915.

On 25 February 1915 U-6 left Germany for operations in the English Channel. She reached Cap Gris Nez on 27 February, and on 28 February was preparing to carry out an attack on the British steamer Thordis off Beachy Head, when the submarine's periscope was spotted by the merchant ship, which rammed U-6, damaging U-6's periscope. This forced the submarine to abandon her patrol and return to base.

U-6 operated in the North Sea between 7 and 20 April 1915. Based in Heligoland, she left for the British east coast. On 11 April she launched two torpedo attacks against a steamer off Aberdeen; both attacks failed. For the next three days U-6 observed shipping in the area until she successfully attacked and sank two steamers on 14 April. On 18 April she took the British trawler Glencarse (188 tons) as a prize and headed back to base, arriving in Heligoland on 21 April 1915.

Leaving Heligoland again on 17 July 1915, U-6 sank a Swedish sailing ship of 422 tons carrying timber to Britain on 19 July. On 21 July she took two Swedish steamers as prizes and set two more sailing ships (757 tons) carrying timber to Britain on fire. Three Norwegian sailing ships were burnt on 25 July. After a brief brush with a Q ship the next day, a Swedish steamer and three Danish sailing ships were burned. When she ran low on fuel, U-6 returned to base on 29 July reaching Heligoland the next day.

On 9 September 1915 U-6 sailed for what would be her final cruise. Burning two Norwegian sailing ships carrying timber to Britain on 10 September, U-6 took a Norwegian steamer as prize. Two days later a Norwegian motor vessel was searched and sunk off Kristiansand. On 14 September U-6 met with U-20.

In the afternoon on 15 September 1915, U-6 was attacked by a British submarine with two torpedoes. Evasive manoeuvres were only partly successful. While the first torpedo missed, the second struck U-6 right in front of the conning tower, sinking her instantly. Except for five men on the conning tower all of U-6's crew perished. According to Oberleutnant z.S. Beyer, officer of the watch at the time of her sinking, the smoke from U-6's paraffin engines made the commander of the Royal Navy submarine aware of her presence and enabled him to get into launching position.

Date	Ship Name	Nationality	Tonnage (GRT)	Fate
14 April 1915	Folke	Sweden	1,352	Sunk
14 April 1915	Glencarse	United Kingdom	188	Captured as prize
14 April 1915	Vestland	Denmark	3,392	Sunk
19 April 1915	Capella	Sweden	422	Sunk
21 July 1915	Anvers	Norway	862	Captured as prize
21 July 1915	Madonna	Sweden	455	Sunk
22 July 1915	Fortuna	Sweden	203	Sunk
25 July 1915	G. P. Harbitz	Norway	673	Sunk
25 July 1915	Harboe	Norway	388	Sunk
25 July 1915	Sognedalen	Norway	644	Sunk
26 July 1915	Elna	Denmark	78	Sunk
26 July 1915	Emma	Sweden	687	Sunk
26 July 1915	Marie	Denmark	173	Sunk
26 July 1915	Neptunus	Denmark	143	Sunk
10 September 1915	Presto	Norway	206	Sunk
11 September 1915	Wansbeck	Norway	462	Sunk
11 September 1915	Randulf Hansen	Norway	1,287	Captured as prize
12 September 1915	Bien	Norway	120	Sunk
13 September 1915	Norte	Norway	216	Sunk