K XVIII was one of five K XIV-class submarines built for the Royal Netherlands Navy. She served during World War II.

The submarine was laid down in Rotterdam at the shipyard of Fijenoord on 10 June 1931. The launch took place on 27 September 1932. On 23 March 1934 the boat was commissioned in the Dutch navy. From 20 June to 1 August 1934 K XVIII, K XVII, Hertog Hendrik, Evertsen and Z 5 made a trip to the Baltic Sea. The ports of Gdynia, Königsberg, Riga and Copenhagen were visited.

On 14 November 1934 the boat was sent to the Dutch East Indies, where she arrived on 11 July 1935 in Surabaya. During this journey Felix Andries Vening Meinesz conducted gravity measurements, as he had previously done aboard the USS S-21 in the Caribbean. On 6 September 1938 she participated in a fleet show at Surabaya. The show was held in honor of the Dutch Queen Wilhelmina of the Netherlands who celebrating her fortieth year as head of state. More than twenty navy ships participated in the show.

In the war K XVIII sank several Japanese ships. On 24 January 1942 the boat attacked the submarine chaser CH-12, but the torpedo ran too low as Ch-12 counter attacked with depth charges and badly damaged K XVIII. While still under repair at Surabaya she was scuttled on 2 March 1942 in order to prevent the Japanese from capturing the boat. K XVIII was raised by the Japanese in 1944 and converted into an air warning picket hulk and deployed in the Madura Strait. On 16 June 1945 the hulk was sunk by the British submarine Taciturn.

Ships sunk and damaged by K XVIII.

Date	Ship name	Nationality/Type	Tonnage (GRT)	Fate
23 January 1942	?	Japanese destroyer	1400	Sunk
23/24 January 1942	Tsuruga Maru	Japanese cargo ship	6988	Sunk
24 January 1942	P 37 or # 12	Japanese patrol boat or Submarine Chaser	935 or 291	Damaged

06°48′S 112°47′E / 6.800°S 112.783°E / -6.800; 112.783