The Type 23 frigate is a class of frigate serving with the Royal Navy of the United Kingdom. All the ships are named after British Dukes, thus the class is also known as the Duke class.

The first Type 23 was commissioned in 1989, and the sixteenth, HMS St Albans was launched in May 2000 and commissioned in June 2002.

Of the sixteen Type 23 vessels constructed, thirteen remain in service with the Royal Navy.

The Type 23 was initially conceived as an anti-submarine warfare platform, with a Westland Lynx or EH 101 Merlin helicopter and a towed array sonar, to replace the Leander-class frigate. They were to hunt and destroy Soviet submarines in the North Atlantic, and it was initially proposed that they would not mount defensive armament. Instead the Sea Wolf missile system was to be carried by the Fort Victoria-class replenishment oiler, one of which was to support typically four Type 23s. The Forts would also provide servicing facilities for the force's helicopters; the Type 23 would have facilities only for rearming and refuelling them.

There were some early problems, e.g. the Command System was not operational as quickly as had been planned, but these have been overcome and the RN has made steady improvements to weapons and sensors in the ships over the years since first introduction.

From 1999, the Lynx helicopter was replaced on some of the vessels by the EH 101 Merlin helicopter. These ships are powered by a CODLAG system (Combined diesel-electric and gas-turbine propulsion) and the diesel-electric is used for minimum underwater noise during ASW operations.