'Plenaps' was the Allied plan for the British, Dutch and US naval forces in the Far East to operate jointly in the event of war with Japan (December 1941).

The plan was not formally endorsed by either the British or the US government, and was therefore an extemporised theatre-level expedient. In the event the British and Dutch co-operated closely (as laid down in the ABD-2 scheme and the Anglo-Dutch proposals of 27 April 1941), while the Americans operated separately for the purpose of ensuring the defence of the Philippine islands group, though maintaining touch with the British and Dutch in accordance with the ABC-1 agreement.