Matias Fonseca (born 12 March 2001) is a professional footballer who plays as a forward for Argentine Primera División side Instituto. Born in Italy, he represented them at youth international level before switching his allegiance to Uruguay.
Born in Naples, Fonseca was formed as a player on Como and Inter Milan youth system.
After his promotion to first team on 2021, Fonseca was loaned to Serie C club Pergolettese. He made his professional debut on 11 September 2021 against Pro Sesto.
On 31 January 2023, Fonseca signed with Montevideo Wanderers for the 2023 season.
Fonseca made his debut for Italy U19 on 15 January 2020 against Spain U19.
In January 2024, Fonseca was named in Uruguay's squad for the 2024 CONMEBOL Pre-Olympic Tournament. In May 2024, he was named in the first ever Uruguay A' national team squad. He made his Uruguay A' debut on 31 May 2024 in a goalless draw against Costa Rica.
Matias is son of former Uruguayan international Daniel Fonseca. His brother Nicolás is also a footballer.