Count of Arraiolos (in Portuguese Conde de Arraiolos) is a Portuguese title granted, in 1377 by King Fernando I of Portugal, to Dom Álvaro Pires de Castro, a Galician noble, brother of Inês de Castro (King Pedro I of Portugal 2nd wife). Álvaro Pires de Castro was already Count of Viana (da Foz do Lima) when he received this new title.

Following Álvaro's death, King John I of Portugal gave this County to his Constable, Nuno Álvares Pereira in 1387, who ceded it, in 1422, to his grandson, Fernando of Braganza.

The title of Count of Arraiolos became a subsidiary title of the House of Braganza when Fernando became 2nd Duke of Braganza (1461).

List of the Counts of Arraiolos

1. Álvaro Pires de Castro (1310-1384), also 1st Count of Viana (da Foz do Lima) and 1st Constable of Portugal;
2. Nuno Álvares Pereira (1360-1431), also 7th Count of Barcelos, 2nd Count of Ourém and 2nd Constable of Portugal;
3. Fernando I, Duke of Braganza (1403-1478).

(for the list of holders after this date, see Duke of Braganza)