Francisco de Vargas y Mejía (b. Madrid, 1500; d. at the Hieronymite monastery of la Cisla in 20 April 1566) was a Spanish diplomat and ecclesiastical writer.

I am sure your Highness will have had more recent news from the Duke of Alva, who has taken the field with an excellent army and has penetrated so far into the Pope's territory that his cavalry is raiding up to ten miles from Rome, where there is such panic that the population would have run away had not the gates been closed.

The two Carafa brothers, the Cardinal and Count Montorio, do not agree, and they and Piero Strozzi are not on as good terms as they were in the past.

However, Vargas again obtained the confidence of Pius IV, and was commissioned by the latter in 1563 to prepare an opinion on the question of the papal jurisdiction, as to which the Council of Trent had become involved in a dispute.

His reports and letters contain important information on the doings of the Council of Trent, but he cannot be regarded as an entirely unprejudiced witness, because his interest was that of a diplomat in the service of his king.

After his return to Spain he was made state councillor, but soon resigned all his offices and retired to the Hieronymite monastery of la Cisla near Toledo, in order to prepare himself for death.