Algueirão – Mem Martins (Portuguese pronunciation: [alɣɐjˈɾɐ̃w ˈmɐ̃j mɐɾˈtĩʃ]) is a Portuguese civil parish, in the municipality (concelho) of Sintra, and part of the Lisbon Metropolitan Area.

It was elevated from the status of village to town on 1 February 1988.

[1] The toponym 'Algueirão' dates back to the Muslim presence in the region between the 8th and 12th centuries.

It evolved from the Arab term al-gueirān, meaning the caves.

'Mem Martins' is a proper name of uncertain origin, consisting of the medieval given name Mem and the patronymic Martins, likely after one of the first property owners in the region following the Portuguese conquest of Lisbon and Sintra.