'Prefix' was a British two-part naval undertaking, in parallel with 'Muscular', against German convoys along the west coast of German-occupied Norway by the escort carrier force of Admiral Sir Bruce Fraser’s Home Fleet (24/29 March 1944).

The forces under the command of Rear Admiral R. R. McGrigor for both parts of this undertaking were the escort carriers Nairana, Puncher, Queen and Searcher, the light anti-aircraft cruisers Bellona and Dido, and the destroyers Carysfort, Onslow, Serapis, Zealous, Zest and Canadian Haida and Iroquois.

The two escort carriers used in 'Prefix' were Queen and Searcher, with the usual escort of one cruiser and several destroyers. The weather was against the undertaking, which therefore achieved no successes against shipping. 'Prefix I' took the form of a day attack in the Leads between Trondheimfjord and Kristiansund North, and 'Prefix II' resulted in the bombing of two ships and attacks on anti-aircraft positions at Ålesund and a radio station at Vikero.