HMS Lancaster is a Duke-class Type 23 frigate of the Royal Navy, launched by Queen Elizabeth II on 24 May 1990. The ship is known as "The Queen's Frigate", the Duke of Lancaster being a subsidiary title of the Sovereign. Being the third ship in the Type 23 class, Lancaster was originally allocated the pennant number F232 until it was noted that the 232 is the Royal Navy report form for groundings and collisions and therefore considered unlucky. She is one of the few ships left in the fleet with some female officers but mess decks which are men-only. It is quite common when she has returned from long operations that she is flown over by the Avro Lancaster bomber which is part of the Battle of Britain Memorial Flight based at RAF Coningsby.

The Type 23 frigate or Duke class is a class of frigates built for the United Kingdom's Royal Navy. The ships are named after British Dukes, thus leading to the class being commonly known as the Duke class. The first Type 23, HMS Norfolk, was commissioned in 1989, and the sixteenth, HMS St Albans was commissioned in June 2002. They form the core of the Royal Navy's destroyer and frigate fleet and serve alongside the Type 45 destroyers. They were designed for anti-submarine warfare, but have been used for a range of uses. Ten Type 23 frigates remain in service with the Royal Navy, with three vessels having been sold to the Chilean Navy, one being retired in 2021, and two being retired in 2023.