The Host  is a 2006 monster film directed and co-written by Bong Joon Ho. It stars Song Kang-ho as food stand vendor Park Gang-du whose daughter Hyun-seo (Go Ah-sung) is kidnapped by a creature dwelling around the Han River in Seoul. Byun Hee-bong, Park Hae-il, and Bae Doona appear in supporting roles as Gang-du's father, brother, and sister, respectively, who help Gang-du escape quarantine against an alleged virus derived from the monster and search for his daughter. Considered a co-production between South Korea and Japan, the film was produced by independent studio Chungeorahm Film and presented by its South Korean distributor Showbox and the Japanese investor Happinet.

Bong had dreamed of making a monster movie since his adolescence, inspired by the Godzilla and Ultraman franchises. The catalyst for The Host was the McFarland incident that occurred in February 2000, when an American civilian working on a military base in South Korea ordered the disposal of formaldehyde down a drain leading to the Han River. Bong devised the story of a monster resulting from this incident and proposed it two years later. In 2003, he started scripting The Host with Ha Joon-won; Baek Chul-hyun joined the pair to revise the script in December 2004. Principal photography lasted from June 2005 to January 2006, mostly taking place in Seoul along the Han River. New Zealand-based special effects company Wētā Workshop modeled the creature and the American studio The Orphanage handled the visual effects. Of the film's $11 million budget, $4.5 million was spent on the over 100 visual effect shots.

An unfinished cut of The Host debuted at the 59th Cannes Film Festival on May 21, 2006, as part of the Directors' Fortnight. The finished film was released in South Korea on July 27, Japan on September 2, and in the United States on March 9, 2007. It became the highest-grossing South Korean film of all time, earning $89–97 million worldwide. Many critics praised The Host as among the best films of 2006 or 2007. The film received several accolades, including the inaugural Asian Film Award for Best Film. A sequel and an American remake were later announced, but neither materialized.

In recent years, The Host has been called one of the best monster and horror films of the 21st century thus far, and it has been listed among the greatest science fiction films ever made. It is regarded as a landmark of Korean cinema and remains among South Korea's highest-grossing films. Some retrospective reviews felt that The Host has grown in relevance as COVID-19 restrictions reflected elements of the film.