Sóror Mariana Alcoforado (Santa Maria da Feira, Beja, 22 April 1640 – Beja, 28 July 1723) was a Portuguese nun living in the convent of the Poor Clares (Convento de Nossa Senhora da Conceição, Convent of Our Lady of the Conception) in Beja, Portugal. Debate continues as to whether Mariana was the real Portuguese author of the Letters of a Portuguese Nun (comprising five letters). Her purported love affair with the French officer Noël Bouton, Marquis de Chamilly and later Marshal of France, has made Beja famous in literary circles, mainly in Portugal and France.