Josep Martínez Riera was born on 27 May 1998 in Alzira, Valencia, Spain. He developed at Barcelona's La Masia academy before joining UD Las Palmas in 2017, where he gained senior experience in Spain's lower divisions.
In 2020 he moved to RB Leipzig, contributing to the squad that won the 2021-22 DFB-Pokal. He then went out on loan to Genoa during their 2022-23 Serie B promotion campaign, performing well enough that the move was made permanent and he settled into Serie A as Genoa's first-choice keeper.
Inter Milan signed him in July 2024 to be the long-term partner of Yann Sommer in their goalkeeping rotation. He made his competitive Inter debut in December 2024 in the Coppa Italia against Udinese and his Serie A debut on 22 February 2025, keeping a clean sheet in a 1-0 win against his former club Genoa after Sommer was injured. He was part of Inter's 2025-26 Serie A title-winning squad.
Internationally, Martínez has earned senior caps for Spain at U21 level and one senior friendly cap for the full national team in 2021.
A modern goalkeeper with strong shot-stopping and confident distribution, Martínez is widely seen as one of the best young Spanish keepers of his generation, and at Inter he is trusted to step in for Sommer with minimal drop in level.