HMS Cyclops (F31) was a submarine repair and depot ship of the Royal Navy.

She was originally the passenger liner Indrabarah sister ship to Indralema, built by Laing, for the Indra Line Ltd then bought by The Admiralty, while she was building.

Between the wars HMS Cyclops served in Malta and was in reserve at the start of the Second World War before returning to Home Waters in late 1939 as the depot ship for the Royal Navy's 7th Submarine Flotilla[4] based in Rothesay.

Between November 1939 and May 1940 Cyclops was the depot ship for the 3rd Submarine Flotilla,[5] based at Parkeston Quay, Harwich Harbour.

Cyclops was equipped with a distillation plant for fresh water, machinery, carpenters' and blacksmiths' shops, coppersmiths', iron and brass foundries.