Theri (transl. Spark) is a 2016 Indian Tamil-language action thriller film directed by Atlee and produced by Kalaipuli S. Thanu under the banner V Creations. Loosely inspired from the 1990 Tamil film Chatriyan and 2013 Hollywood film Homefront, the film stars Vijay, Samantha Ruth Prabhu, Amy Jackson, Nainika. The music was composed by G. V. Prakash Kumar, with cinematography handled by George C. Williams and editing by Ruben. In the film, a former cop is on a mission to protect his daughter from his past enemies.

The film marked Kumar's second directorial after Raja Rani (2013), whose success impressed Vijay enough to work with the director. Atlee came up with the script, which was an "emotional action thriller film," and a formal announcement was made in September 2014. After post-production work and a formal launch ceremony in June 2015, the film began production in Chennai in early July. The film was halted twice due to the Film Employees Federation of South India's strike and the heavy flooding in Chennai. In addition, poor climatic conditions in China meant that the team had to abandon their idea of filming sequences there and instead opt to shoot in Bangkok. Despite the difficulties, the film was completed in January 2016.

Theri was released on 14 April 2016 to positive reviews from critics and grossed ₹150 crore (US$17 million) against a budget of ₹75 crore (US$8.7 million). The film emerged as the second highest-grossing Tamil film of 2016. It further won three SIIMA Awards, three IIFA Utsavam Awards, two Ananda Vikatan Cinema Awards and nine nominations at the 64th Filmfare Awards South. The film was adapted into Sinhala as Goree (2019) and Assamese as Ratnakar (2019). The film was remade in Hindi as Baby John and is currently being remade in Telugu as Ustaad Bhagat Singh. It is currently considered one of the most popular films in Vijay's career, and its multiple re-runs on television channels have contributed to its popularity.