Guillermo Arriaga Jordán (b. 1958) is an Academy Award-nominated, award-winning Mexican author, screenwriter and producer. He received the 2005 Cannes Film Festival Best Screenplay Award for The Three Burials of Melquiades Estrada.

Arriaga was born in Mexico City and spent his childhood in one of the most violent sectors of the metropolis. At the age of 13 he lost the sense of smell after a brutal street fight that would later serve as inspiration for some of his work.

Before engaging in his writing career, Arriaga tried out a variety of jobs and professions, amongst which were that of boxer, basketball player and professional soccer player.

He completed a B.A. in Communications and a M.A. in Psychology at the Ibero-American University, where he taught several courses in media studies before joining the ITESM. Self-defined as “a hunter who works as a writer,” he authored Amores Perros, received a BAFTA Best Screenplay nomination for 21 Grams and received the 2005 Cannes Best Screenplay Award for The Three Burials of Melquiades Estrada. Arriaga also had an acting cameo in the latter film as a bear hunter.

While teaching at the Universidad Iberoamericana Guillermo Arriaga met future film director Alejandro González Iñárritu and decided to make a feature length, multiplot film set in Mexico City. The result was Amores Perros (1999), one of the most heavily praised films in the recent history of Mexican cinema. The film's gritty look at the underbelly of Mexican life won an Oscar nomination for "Best Foreign Film" as well as a BAFTA Film Award for "Best Film not in the English Language," the "Critics Week Grand Prize" and "Young Critics Award" at the 2000 Cannes Film Festival as well as many other awards from festivals and societies around the world.

The success of "Amores Perros" won Arriaga and Iñárritu an invitation to the U.S. to work on the Universal/Focus feature film 21 Grams, starring Benicio del Toro, Naomi Watts and Sean Penn. Watts and del Toro received Academy Award nominations for their performances.

Iñárritu and Arriaga collaborated on a third movie, Babel, to form a trilogy with his first two pictures focusing on the theme of death. However, friction between writer and director led to Iñarritu banning Arriaga from attending the 2006 Cannes screening of Babel. Nevertheless, Inarritu and Arriaga both received Academy Award nominations for their work. Their future as a creative couple however, looks bleak and it is unlikely that the two will ever work together again.

On January 19, 2007 the film adaptation of his book El Búfalo de la Noche directed by Jorge Hernandez Aldana premiered at the Sundance film festival. It features an original score by Omar Rodriguez-Lopez of The Mars Volta. The main title sequence for this movie was created by Canadian studio Mucho Motion and One Size from the Netherlands.

In 2007, Arriaga became a somewhat political figure in Mexico when relating to cinema and specifically when relating to screenwriters in general. An award-winning screenwriter, Arriaga has repeatedly stated that he hates being called a "screenwriter" and that he hates screenplays being referred to as such. He claims that he and all other screenwriters are writers, and the title of screenwriter diminishes the work of screenwriters. He now continuously advocates for screenwriters being referred to as "writers" and screenplays being referred to as "Works of Film".

Other screenwriters in Mexico and around the world have not been very pleased with his actions, but his status as one of Mexico's most renowned screenwriters has overshadowed the opinions of all other screenwriters.

In 2007, he was one of 10 Mexican Oscar-nominees. The others were Alejandro González Iñárritu, Adriana Barraza, Guillermo del Toro, Alfonso Cuarón, Guillermo Navarro, Emmanuel Lubezki, Eugenio Caballero, Pilar Revuelta (I) and Fernando Cámara (I).

Wrote Alejandro González Iñárritu's first three feature films: Amores perros (2000), 21 Grams (2003) and Babel (2006).

One of 115 invitees to join AMPAS in 2007.

His novel El Bufalo de la Noche (The Night Buffalo) was adapted into a feature film by director Jorge Hernandez Aldana.