'Crucible' was a British unrealised operation to land airborne forces on the Ile d’Ouessant off the western tip of the Brittany peninsula in German-occupied France (September 1942).

The island was potentially of considerable tactical and operational significance as it commands the seaward approaches to the port city of Brest, but while its initial seizure might have been feasible, its subsequent retention for all but the shortest of times would have been impossible by reason of the closeness of German air, land and sea forces and the distance of the island from any form of support from the UK.