Xabier Alonso Olano (Basque: [ˈʃaβi aˈlons̺o oˈlano], Spanish: [ˈʃaβj aˈlonso oˈlano]; born 25 November 1981) is a Spanish professional football manager and former player who is the head coach of La Liga club Real Madrid. Widely regarded as one of the greatest midfielders of his generation, he was known for his range of 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 on to 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.

Alonso was born in the small town of Tolosa, Gipuzkoa, Basque Country, into a family known for its footballing prowess. His father, Periko Alonso, won La Liga twice in successive seasons with Real Sociedad and a third time after he joined Barcelona. He also featured in the national team, winning 21 caps over the course of his career.

Alonso lived in the city of Barcelona for the first six years of his life and moved to San Sebastián (Donostia) thereafter. It was here that his passion for football began as he whiled away his childhood played at Playa de la Concha (Shell Beach). On the Basque sands, Alonso befriended a fellow resident of Calle Matia, Mikel Arteta, and the two would battle each other in exhibitions of technical ability. He was immersed in football and his father would often bring him and his older brother, Mikel, to Sabadell's training ground to practise together. Alonso was influenced by his father's playing, taking more pleasure in passing the ball well than shooting at goal. At an early age, he decided to play as a defensive midfielder, a role which helped him learn how to distribute the ball well. This talent would later prove to be an integral part of his club and international career.

Alonso and Arteta were ambitious and dreamed of playing alongside each other for Real Sociedad when they were older. Though they attended different schools, the two young players joined forces at the local youth side Antiguoko, playing games at the weekend. Their performances attracted the attention of scouts from top Spanish sides and the young Donostiarras separated ways, ending nine years of friendly rivalry, as Alonso went to Real Sociedad and Arteta moved to Catalan giants Barcelona. Alonso's move to Real Sociedad, however, was not a companionless one, as his older brother Mikel, who had also become an adept player, joined the club together with him.

Alonso quickly progressed through the youth ranks and the reserve team at Real Sociedad (winning the regionalised fourth tier in his single season with the latter) and impressed enough to earn a first team debut at the age of 18. He made his first senior appearance against Logroñés on 1 December 1999 in a Copa del Rey match. Alonso failed to make another appearance in the season but the following year brought more opportunities. At the beginning of the 2000–01 season, Javier Clemente sent him to Segunda División team Eibar to gain experience. Alonso's father particularly felt the move to the smaller club improved him as a player. A quick turnover of managers, however, including a two-month period with Periko Alonso in charge, left Real Sociedad in a dire situation. By January 2001, Real Sociedad were bottom of the league and its new manager, John Toshack, turned to the prodigious Alonso in the hope of reversing the team's fortunes. In a surprise move, the Welsh manager made the 20-year-old the team captain, a position traditionally held by more senior players. By the end of the season, Sociedad had climbed out of the relegation zone and finished in 14th place. Toshack lauded Alonso, stating that the impression he had on the team was exceptional, especially for a player from the youth team.