Thani Oruvan (transl. The Sole One) is a 2015 Indian Tamil-language action thriller film directed by Mohan Raja, who co-wrote the script with Suresh and Balakrishnan. It is produced by Kalpathi S. Aghoram, S. Ganesh and S. Suresh under AGS Entertainment. The film stars Ravi Mohan and Arvind Swamy in lead roles. Nayanthara, Thambi Ramaiah, Ganesh Venkataraman, Harish Uthaman, Sricharan, Rahul Madhav, Nagineedu, Madhusudhan Rao, Saiju Kurup, Nassar and Mugdha Godse plays supporting roles.

The plot revolves around IPS Officer Mithran, who wants to arrest Siddharth Abhimanyu, an affluent scientist who uses secret illegal medical practices for profit. Thani Oruvan was Raja's original story concept, unlike his previous ventures, which were remakes. Principal photography commenced on 6 December 2013, with filming took place in various locations including Chennai, Bangalore, Hyderabad, Dehradun, Mussoorie, and other locations.

The cinematography and editing were handled by Ramji and Gopi Krishna respectively. The music was composed by Hiphop Tamizha, in which the soundtrack album received positive reviews. The film was released on 28 August 2015 to critical acclaim, with praise for the direction, screenplay, storyline, pacing and the performances of Jayam Ravi and Thambi Ramaiah but especially Aravind Swamy. It was a commercial success, and also became one of the highest grossing Tamil films of the year.

The film was remade in Telugu as Dhruva (2016), and in Bengali as One (2017). After 8 years following the huge success of the film, Mohan Raja announced the sequel, Thani Oruvan 2, reuniting with Ravi and Nayanthara.