'Thruster' (i) was a British unrealised plan for the opposed seizure of the Azores islands group, a Portuguese possession in the Atlantic Ocean, in the event that Germany moved against Spain and Portugal (June 1941).

The operation was schemed in concert with 'Springboard' against Madeira, another Portuguese possession, and 'Puma' (i) against the Canary islands group, a Spanish possession. For much of 1941 forces were kept on the alert for any or all of these operations in the UK, Gibraltar or Sierra Leone. In July 1941 the three separate operations were combined into the single 'Pilgrim', to use some 24,000 men and all available amphibious capability.