Unai Simón Mendibil (born 11 June 1997) is a Spanish footballer who plays as a goalkeeper for La Liga club Athletic Bilbao and the Spain national team.

[12] He initially appeared to be behind the older Álex Remiro in the queue for selection,[13] but made his professional – and La Liga – debut five days later, starting in a 2–1 home win against CD Leganés.

[16] However, when Herrerín regained full fitness in October 2018 he was made the starting goalkeeper, with Simón's only appearances over the subsequent four months coming in the Copa del Rey.

[17] He continued his strong form throughout the season, missing two fixtures with illness and completing 33 matches in the league, conceding 29 goals[18] to finish third in the Zamora Trophy rankings.

[27][28][29] On 10 November 2023, in "one of his best moments as a professional",[30] he saved a penalty from Celta de Vigo striker Iago Aspas to keep the score level in a game his team went on to win.

[31] On 16 March 2024, he stopped another penalty from Luis Rioja of Alavés, starting a move which culminated in a goal for Athletic forty seconds later as they again went on to win;[32] in addition, Simón consolidated his position as leader in the Zamora Trophy with his 15th clean sheet in the league.

[41] Despite having made an error which led to a goal at club level a few days earlier, he was selected for his full debut on 11 November 2020, playing the entirety of a friendly against the Netherlands.

[43] Having displaced David de Gea as first-choice, he started all of the team's matches, and caused an own goal in the 5–3 last-16 win over Croatia when he was unable to control a long backwards pass by Pedri.

[50] They had better fortune in the 2023 UEFA Nations League final six months later, where another 0–0, against Croatia, was followed by a 5–4 win in the shootout to claim the title, Simón blocking attempts from Lovro Majer and Bruno Petković.