The Host (Korean: 괴물; RR: Goemul; lit. Monster) is a 2006 monster film written and directed by Bong Joon-ho. It stars Song Kang-ho as vendor Park Gang-du whose daughter Hyun-seo (Go Ah-sung) is kidnapped by a creature dwelling around the Han River. Byun Hee-bong, Park Hae-il, and Bae Doona appear in supporting roles as Gang-du's father, brother, and sister respectively. A South Korean-Japanese co-production, the film was produced by Chungeorahm Film with Showbox and Happinet presenting.

Bong had been conceiving a monster movie since his adolescence, inspired by the Godzilla and Ultraman franchises. The catalyst for The Host was a scandal that occurred in 2000, in which an American commanded 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, and directed a short film set around the Han River featuring Byun. Baek Chul-hyun joined Bong and Ha for revision in December 2004. Principal photography mostly took place on location near the Han River. Wētā Workshop modeled the film's creature and 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 and Japan on September 2. It became the highest-grossing South Korean film of all time, earning $89.4–92.6 million worldwide. Many critics praised The Host as among the best films of 2006 or 2007. The film also won several accolades, including the 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 hailed as one of the best monster and horror films of the 21st century, and listed among the greatest science fiction films ever made. Seen as a landmark of South Korean cinema, it remains among the country's highest-grossing films. The film had a resurgence in popularity upon Bong gaining further international recognition for Parasite (2019). Some retrospective reviews have felt that The Host has grown in relevance as elements came to reflect the COVID-19 pandemic.