Spanish defender Aritz Elustondo Irribarria (born 28 March 1994), a native of Beasain in Gipuzkoa, Basque Country, began his football journey in the youth academy of Real Sociedad. In July 2012, he was loaned to Tercera División side SD Beasain, where he made his senior debut.

He returned to Real Sociedad in the summer of 2013 and joined the club’s reserve team, which competed in the Segunda División B. On 31 January 2014, he signed a new contract that kept him at the club until 2016.

Elustondo made his first-team debut on 14 January 2015, starting in Real Sociedad’s 2-2 home draw against Villarreal in the Copa del Rey Round of 16. Three days later, he made his La Liga debut in a 1-0 home defeat to Rayo Vallecano.

He scored the first goal of his professional career on 31 January 2015 in an away match against Real Madrid. A year later, having established himself under head coach Eusebio Sacristán, he extended his contract with the club until 2020.

Elustondo remained a key member of the Real Sociedad squad in the years that followed, signing further contract extensions in February 2018 (until June 2022) and again in August 2020 (until June 2024). On 30 November 2025, he reached the milestone of 300 official appearances for the club in a league match against Villarreal.

His long spell at Real Sociedad came to an end following the conclusion of the 2025-26 season. He departed after making 313 official appearances in all competitions and played his part in the club’s Copa del Rey triumph during his final campaign, featuring in four matches in the competition.

At international level, Elustondo has represented the Basque Country national team and has also earned caps for Spain’s Under-21 national team.