The siege of Lisbon, from 1 July to 25 October 1147, was the military action against the Muslim-ruled Taifa of Badajoz that brought the city of Lisbon under the definitive control of the new Christian power, the Kingdom of Portugal.

Lisbon is the capital and largest city of Portugal, with an estimated population of 548,703 as of 2022 within its administrative limits and 2,871,133 within the metropolis. Lisbon is mainland Europe's westernmost capital city and the only one along the Atlantic coast, the others being on islands. The city lies in the western portion of the Iberian Peninsula, on the northern shore of the River Tagus. The western portion of its metro area, the Portuguese Riviera, hosts the westernmost point of Continental Europe, culminating at Cabo da Roca.