Two ships of the Royal Navy have been named HMS P38.

• HMS P38 (1917), a P-class patrol boat launched in 1917. Renamed HMS Spey on 11 December 1925 and assigned to fishery protection, the vessel was sold in May 1938.
• HMS P38 (1941), a U-class submarine launched in July 1941 and sunk on 23 February 1942 by the Italian torpedo boat Circe north of Tripoli, Libya.

• Colledge, J. J.; Warlow, Ben (2006) [1969]. Ships of the Royal Navy: The Complete Record of all Fighting Ships of the Royal Navy (Rev. ed.). London: Chatham Publishing. ISBN 978-1-86176-281-8.
• "HMS P.38 1917-2-10". Cyldebuilt Warships. Archived from the original on 26 September 2007. Retrieved 11 March 2007.{{cite web}}: CS1 maint: unfit URL (link)
• "Submarine losses 1904 to present day". Royal Navy Submarine Museum, Gosport. Archived from the original on 2 January 2007. Retrieved 11 March 2007.
• "HMS P 38 (P 38)". uboat.net. Retrieved 11 March 2007.