HNLMS K X was one of the three K VIII-class submarines of the Royal Netherlands Navy, built to serve as a patrol vessel in the Dutch colonies.

[2] The submarine was ordered from the Koninklijke Maatschappij de Schelde shipyard at Vlissingen on 27 June 1917, but not laid down until 1 November 1919, and finally launched on 2 May 1923.

[2] In February and March 1941 K X, K VIII and K XIX patrolled the Sunda Strait while based at Tanjung Priok, while the Admiral Scheer was sinking Allied merchant shipping in the Indian Ocean.

Short on battery power and with faulty steering gear and only one diesel engine operating the submarine returned to Surabaya for repairs.

[2] Crewmen from K X, K IX and K XII were sent back to England to crew the submarine Haai, then under construction as HMS Varne (P66), but their unescorted passenger ship MV Abosso was sunk by the German U-boat U-575 north of the Azores on 29 October 1942,[3] and only four of the 34 Dutch Navy men aboard survived.