José João da Conceição Gonçalves Mattoso GOSE (22 January 1933 – 8 July 2023) was a Portuguese medievalist and university professor.

[1][2] He earned his doctoral degree in medieval history from the Catholic University of Leuven, in Belgium, in 1966 (with a thesis on the abbey of Pendorada - "L'Abbaye de Pendorada  : des Origines à 1160"), while he was Benedictine monk at the Abbey of Singeverga.

His works include, among others, "Ricos homens, Infanções e Cavaleiros" (on the medieval society), "Fragments of a Medieval Composition" (in response to the arguments of Antonio Borges Coelho), and "Identification of A country Essay on the Origins of Portugal (1096–1325)" (Vol.

He was also awarded the Fernando Pessoa Prize in 1987, among other important distinctions.

Mattoso acted as the scientific editor of a History of Portugal (1993–1995) in eight volumes.