The oldest and most important university in Portugal is the University of Coimbra.

An excerpt from the article 37 facts about Portugal

It was the only institution of this type in the country until the beginning of the 20th century. It was founded in 1290 as a study generale (a name given in the Middle Ages to some schools of international importance) by Denis of Portugal, the Farmer King (the sixth king of Portugal from 1279). The university was initially located in Lisbon, but as a result of a conflict between the city's inhabitants and the academic community, the university was moved to its current location in 1308. In 2013, the university was included on the UNESCO World Heritage List.