Ajith was born on 1 May 1971, in Hyderabad, India. His father P. Subramaniam is a Brahmin from Palakkad,Kerala. and his mother Mohini is Sindhi and is from Kolkata, West Bengal. He dropped out of Asan Memorial Senior Secondary School in 1986 before completing his higher secondary.

Ajith created the non-profit organisation “Mohini-Mani Foundation”, named after his parents, in order to promote self-hygiene and civic consciousness and to help ease the problems of urban sprawl. Ajith was the middle son out of three brothers, the others being Anup Kumar, an investor, and Anil Kumar, an IIT Madras graduate-turned-entrepreneur.

Aged 19, Ajith began his acting career and appeared in a song in En Veedu En Kanavar (1990). Later, Ajith was selected by the Telugu film production company Lakshmi Productions, to star in its film; however, shooting was stalled soon after filming began, following the death of the film’s director. 

Ajith then appeared in the low budget Telugu film Prema Pustakam in 1992, which remains his last direct Telugu film to date. His first Tamil film Amaravathi, directed by then newcomer Selva, was a moderate success and his voice was rendered by fellow actor Vikram.

After the release and while training for an amateur motor race, Ajith suffered a fall, injuring his back and underwent three major surgeries resulting in a bed rest for one and a half years. Following the injury in 1993, Ajith played a small role in the Arvind Swamy starrer Paasamalargal, before appearing in a supporting lead role in the family drama Pavithra, which featured him as an ailing patient shown maternal affection from Raadhika.

Following a year of production, Ajith’s Aasal, released in February 2010, taking a grand opening at the box office. The film, which also featured Ajith in dual roles, also failed at the box office despite bigger expectations.

After a second foray into motor racing, Ajith signed a film directed by Venkat Prabhu, titled Mankatha, which notably became his 50th project. The film featured him in a full-length negative role as Vinayak Mahadevan, a suspended police officer with a lust for money.

His performance and his decision to portray a character with negative shade, breaking the stereotype hero image in Tamil cinema, were lauded by critics, with reviewers from Sify and Rediff terming the film as an “out and out Ajith film” that worked “only because of Ajith”.

Heaping praise on the actor’s performance, the former noted that he “rocks as the man with ice in his veins as the mean and diabolic cop” and that he played “the emotionless bad man, to perfection”, while the latter wrote that practically “he carried the whole film on his capable shoulders”. Mankatha became a financially successful venture.

Ajith then starred in Billa II, a sequel to his 2007 film Billa, which released on 13 July 2012. Reviewers appreciated Ajith’s on-screen presence and stunts but blamed him for the choice of story and the director. Eventually, the film performed poorly at the box office.

He starred in Vishnuvardhan’s Arrambam, alongside Arya, Nayantara and Rana Daggubati, which was released on 31 October, and earned positive reviews from both critics and audience. His next film after Arrambam was Veeram, directed by Siva and co-starring Tamannaah, which was released on Pongal 2014, which also earned positive reviews from critics.

Ajith’s next film was Yennai Arindhaal, with Gautham Menon as director. Ajith’s performance as cop was widely praised with a critic calling it “Ajith’s best since Kandukondain Kandukondain“. Ajith was subsequently nominated for the Filmfare Award for Best Actor – Tamil in the 63rd Filmfare Awards South. Ajith worked with Siva again in Vedalam (2015), in which critics praised his performance.

His latest project is Vivegam which received mixed to negative reviews with critics citing illogical scenes and average screenplay. On IMDb, it received a rating of 6 out of 10. Ajith’s next film Viswasam released during Pongal festival of January 2019 is a box office hit having sentiment and action scenes which made it attractive for his fans and family audiences.