Mathías Olivera Miramontes (born 31 October 1997) is a Uruguayan professional footballer who plays as a left-back for Serie A club Napoli and the Uruguay national team.

After progressing through the youth setup, he made his professional debut on 13 February 2016, starting and being booked in a 3–0 away win against River Plate.

In December of that year, he was bought outright by his agent Daniel Fonseca and assigned to Atenas de San Carlos in Segunda División.

[6] In July 2017, Oliveira passed a medical examination at Galatasaray, but eventually did not sign a contract and subsequently returned to Uruguay.

[12] On 7 January 2022, Olivera was named in Uruguay's 50-man preliminary squad for 2022 FIFA World Cup qualifying matches against Paraguay and Venezuela.