Mersal (transl. Zapped) is a 2017 Indian Tamil-language action thriller film directed by Atlee who co-wrote the film with V. Vijayendra Prasad and S. Ramana Girivasan. Produced by Thenandal Studio Limited in the studio's hundredth feature film production, the film stars Vijay in a triple role with S. J. Suryah while Sathyaraj, Vadivelu, Nithya Menen, Kajal Aggarwal, Samantha Ruth Prabhu, Hareesh Peradi, Kovai Sarala and Sathyan appear in pivotal supporting roles. The story revolves around two brothers, who were separated at birth; one is a magician avenging his parents deaths and medical crimes, and the other, a reputed doctor who charges meagre amounts from his patients.

The film's principal photography commenced on 1 February 2017, at Chennai and was completed on September 2017, within 130 working days. Filming took place on Gdańsk, Poland and Jaisalmer, Rajasthan. The background score and soundtrack album were composed by A. R. Rahman, while the cinematography was done by G. K. Vishnu and edited by Ruben.

Mersal was released worldwide on 18 October 2017, coinciding with Diwali. The film received mostly positive reviews with critics praising the performance of Vijay and S. J. Suryah, A. R. Rahman's soundtrack, cinematography, social message and Atlee's direction, but criticised the cliched plot and excessive length. It is also a recipient of various accolades. The film was a commercial success, grossing ₹200 crore (US$25 million) - ₹260 crore (US$33 million) worldwide, becoming the highest-grossing film in Vijay's career at that time as well as one of the highest-grossing Tamil films. The film completed 100-day theatrical run on 25 January 2018. The film was released on 6 December 2018 in China by HGC Entertainment. Due to demand, the film was screened at the largest cinema theatre in Europe Grand Rex, France. The film was screened at the Hainan International Film Festival in Hainan, China and at the Bucheon International Fantastic Film Festival in South Korea.