Alberto San Juan Guijarro (born 1 November 1967) is a Spanish film, stage and television actor. He has featured in films such as Airbag (1997), The Other Side of the Bed (2002), Football Days (2003), Under the Stars (2007), The People Upstairs (2020), and Four's a Crowd (2022). He is the recipient of multiple accolades, including two Goya awards.
Alberto San Juan was born on 1 November 1968 in Madrid, the son of cartoonist and radio announcer Pilar Guijarro Ortiz de Zárate. He was raised in the well-off neighborhood of El Viso. He attended the Colegio Estilo and joined its theatrical group, where he acquainted with his long-term friend Guillermo Toledo. He also spent many of his childhood's summers in Cañamares, province of Cuenca. He studied journalism and worked for two years at Diario 16 before pursuing an acting career. While studying journalism, he acquainted with Antonio de la Torre. At age 24, he joined the Cristina Rota's atelier to train his acting chops.
San Juan landed his big screen debut with a bit part in You Shall Die in Chafarinas (1995). Jointly with Guillermo Toledo, Nathalie Poza and Ernesto Alterio, San Juan founded the theatre group 'Ración de oreja', which merged with Andrés Limas 'Riesgo' into the theatre company . His first film success and main film role was Juanma Bajo Ulloa's Airbag (1997). For his character of Paco, a scoundrel, actors Javier Bardem and Viggo Mortensen were previously considered. In the late 1990s, together with his friends Ernesto Alterio and Guillermo Toledo, he went on to land film credits in Sleepless in Madrid, Washington Wolves, and The Ugliest Woman in the World.
He gained popularity for his supporting role in the musical comedy film The Other Side of the Bed (2002), which also landed him a Goya Award nomination.
For his role as an unsuccessful jazz musician returning to his hometown in Under the Stars (2007), he won the Goya Award for Best Leading Actor.
He was a main promoter of the , a project of political theatre launched in the former premises of the Sala Triángulo in Lavapiés on 4 December 2013.
He starred alongside Mario Casas as a Conservative and homosexual monarchist maître d'hôtel in the aftermath of the Spanish Civil War in the comedy film The Dinner (2025), clinching another nomination for the Goya Award for Best Leading Actor.
Alberto San Juan is known for his left-wing views. He publicly lent support to the United Left ahead of the 2011 Spanish general election. He also endorsed the manifesto that led to the creation of Podemos, presented at the Teatro del Barrio in January 2014. In February 2015, he became a member of the citizens' council of Podemos in Madrid. He later distanced himself from the party, lamenting its breakup due to an "authoritarian concept of internal organisation".
In 2026, he co-signed alongside other Spanish artists a text urging the United Nations and the governments of the world to actively work towards the release from prison of Palestinian leader Marwan Barghouti.