HMS Ambush (P418/S68/S18), was an Amphion-class submarine of the Royal Navy, built by Vickers Armstrong and launched 24 September 1945.

[2] In 1951 she heard and decoded a distress message from HMS Affray, which was sunk with the ultimate loss of all 75 hands.

[5] Ambush was laid down at Vickers Armstrong's Barrow-in-Furness shipyard on 17 May 1945, was launched on 24 September 1945 and completed on 22 July 1947.

Ambush set out from Rothesay on 10 February 1948 on an extended submerged cruise in Arctic waters between Jan Mayen and Bear Island.

The submarine encountered a severe storm, which forced Ambush to the surface as she could not maintain depth control well enough to use the snort, returning to base on 18 March.