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).