Theeran Adhigaaram Ondru (transl. The Warrior: Chapter One) or simply Theeran is a 2017 Indian Tamil-language action thriller film written and directed by H. Vinoth and produced by S. R. Prakashbabu and S. R. Prabhu under the banner Dream Warrior Pictures. Based on the Bawaria robberies, it depicts the nefarious activity of organised dacoity committed in Tamil Nadu during the late 1990s and early 2000s and the subsequent investigation and arrest of robbers by a special investigation team of the Tamil Nadu Police led by Director general of police S. R. Jangid. The film stars Karthi as the titular character Theeran, modelled on Jangid, alongside Rakul Preet Singh and Abhimanyu Singh.

Vinoth had planned for the script based on the incident even before his debut film Sathuranga Vettai (2014), but he later worked on the project in late 2014. To research further, he had met many police officers who handled similar cases. Following an official announcement in December 2016, principal photography commenced in January 2017 and ended that July. Filming took place in many real locations across Chennai and North India, in order to capture the authenticity of the film and has been shot in locations where the incident happened. The film's cinematography was handled by Sathyan Sooryan and the editing was done by Sivanandeeswaran. Ghibran composed the soundtrack and the film score.

The film, distributed and co-produced by Reliance Entertainment, was released worldwide on 17 November 2017 and opened to critical acclaim, praising the direction, writing, cinematography, soundtrack, musical score, and cast performances—especially that of Karthi. The authenticity of capturing the incidents, along with the realistic portrayal of the Tamil Nadu Police in fiction was highlighted and praised by critics. It was a commercial success, grossing ₹96 crore. In addition, the film won the Ananda Vikatan Cinema Awards, Techofes Awards, two Edison and Vijay Awards, each. It received three nominations at the South Indian International Movie Awards and five Filmfare Awards; the film's only win was Critics Best Actor – Tamil for Karthi. A sequel to the film was announced in November 2023.