Duke of Estremera (Spanish: Duque de Estremera) is a hereditary title in the Peerage of Spain, accompanied by the dignity of Grandee and granted in 1538 by Philip II to Ruy Gómez de Silva, 1st Prince of Éboli.

[2][3] Originally, the titles of Estremera and Pastrana were one and the same title, however, the Dukes of Estremera, later Dukes of Pastrana, made themselves known by the two titles, suggesting that they were two different titles.

The Crown distributed the very numerous titles that had been concentrated in his person (thirteen dukedoms, twelve marquessates, thirteen countships and one viscountcy) among his relatives, "forgetting" to grant the Dukedom of Estremera, since it did not exist legally as it was originally replaced by the Dukedom of Pastrana.

It was in 1913, when one of his descendants, Iván de Bustos y Ruiz de Arana, requested the rehabilitation of Estremera, which was accepted and rehabilitated to him as second holder, ignoring that previously there had been eleven Dukes of Pastrana who had also named themselves Dukes of Estremera, and thus confirming that only the first Duke of Estremera had been legally so.

The title makes reference to the town of Estremera in Madrid.