is a Spanish professional football manager and former player who is the head coach of La Liga club Real Madrid. He is regarded as one of the best midfielders of his generation and was known for his passing and long distance shooting. Alonso is also currently considered to be one of the best young managers in the world.

Alonso began his career at Real Sociedad, the main team of his home province Gipuzkoa. After a brief loan period at Eibar, he was appointed as team captain of Real Sociedad and finished runner-up in La Liga in 2002–03 season. He moved to Liverpool in 2004 for £10.5 million and won the UEFA Champions League in his first season, scoring in the final. He later won the UEFA Super Cup the FA Cup and the FA Community Shield. Alonso moved to Real Madrid in 2009 in a deal worth £30 million and won La Liga, two Copa del Rey titles, and another UEFA Champions League. He joined German club Bayern Munich in 2014 and won three Bundesliga titles, including a domestic double in his second season, and retired in 2017.

He made his international debut for Spain in April 2003 and went onto win Euro 2008, the 2010 World Cup, and Euro 2012. He also represented Spain at Euro 2004 and the 2006 World Cup. On 23 June 2012, Alonso won his 100th cap for Spain in the quarter-final of Euro 2012 against France, where he scored both goals in a victory. Alonso retired from international football after the 2014 World Cup. His 114 appearances make him the eighth-most capped player in Spain's history.

Alonso coached Real Madrid's U14 team before being appointed as manager of Real Sociedad B in 2019, where he won promotion to the Segunda División in his second season. Alonso was named head coach of Bayer Leverkusen in 2022 and completed an unprecedented unbeaten domestic double in 2024, winning the club's first ever Bundesliga title and first DFB Pokal since 1993. After two-and-a-half years with the German side, Alonso was appointed as the new head coach of his former club Real Madrid in June 2025.