Dhoom 2 (transl. Blast 2), also known as Dhoom 2: Back in Action, is a 2006 Indian Hindi-language action thriller film directed by Sanjay Gadhvi with script and dialogues written by Vijay Krishna Acharya from a story by Aditya Chopra, who produced the film under Yash Raj Films. The film, a sequel to Dhoom and the second installment of the Dhoom series, stars Hrithik Roshan, Abhishek Bachchan, Aishwarya Rai, Uday Chopra, and Bipasha Basu.

Dhoom 2 was shot primarily in India, Durban and Rio de Janeiro, becoming the first major Hindi film to be shot in Brazil. Dhoom 2 was released on 24 November 2006 to positive reviews from critics, with praise for its action sequences, soundtrack, cinematography and cast performances (particularly Roshan), but criticism for its script and pacing. The film grossed over ₹1.514 billion and became the highest grossing Hindi film of 2006. It became the highest-grossing Hindi film of all time at the time of its release, before being surpassed by Om Shanti Om (2007), and the second highest-grossing Hindi film in overseas markets behind Kabhi Alvida Naa Kehna (2006), also co-starring Bachchan.

At the 52nd Filmfare Awards, Dhoom 2 received 8 nominations, including Best Film, Best Director (Gadhvi) and Best Actress (Rai), and won Best Actor (Roshan). The film also marks the second collaboration between Bachchan and Roshan after Main Prem Ki Diwani Hoon (2003), and the fourth between Bachchan and Rai after Dhai Akshar Prem Ke (2000), Kuch Naa Kaho (2003) and Umrao Jaan (2006); the latter two fell in love during the production of Dhoom 2 and got married the following year.

Dhoom 2 proved to be controversial post release, due to an appeal by the Mumbai city police commissioner to censor the fast-paced action scenes, owing to fears that it would inspire Indian youths to ride their motorcycles rashly, resulting in an increase in the number of road accidents.

A sequel titled Dhoom 3 was released on 20 December 2013. Abhishek Bachchan has since named Dhoom 2 as his favorite film in the series.