'Antrum Yellow/Grey' was a British operation by the Special Operations Executive to organise and instruct groups in the Ålesund area of German-occupied Norway, supply weapons and stores, prepare counter-scorch activities, and plan sabotage against German communications during any invasion or withdrawal (22 September 1944/early 1945).

The two-man party of K. J. Aarsæther and K. Engelsen departed the UK by sea on the night of 22/23 September and replaced Knut Aarsæther, who returned to the UK. Work continued on building up the local organisation and the party was reinforced in October by the arrival of two more men. 'Antrum' was instructed to work closely with the local leadership of the Milorg military resistance organisation, which would be linked with central leadership of the Milorg in Oslo. At the end of October a message was sent via the 'Antrum' radio that Ivar Grande, the informer, should be assassinated, and he was killed on 11 December.