Manmadan Ambu is a 2010 Tamil romantic comedy film directed by K. S. Ravikumar. Written by Kamal Haasan, it stars himself alongside R. Madhavan and Trisha Krishnan in the lead roles, while featuring Ramesh Arvind, Sangeetha, Manju Pillai and Urvashi among others in supporting roles. The film features music composed by Devi Sri Prasad, with several songs written and sung by Kamal Haasan himself, while Manush Nandan and Shaan Mohammed made their debut as cinematographer and editor.

After significant pre-production which included rehearsals of the entire script before filming, the film was extensively shot across Europe and on a cruise ship, whilst scenes were also canned across Chennai and Kodaikanal. It was produced by Udhayanidhi Stalin, Manmadan Ambu released worldwide on 23 December 2010.

Madanagopal/Madan (Madhavan), a wealthy entrepreneur, suspects that his girlfriend, actress Ambujakshi alias Nisha (Trisha) may be having affairs with her colleagues in the film industry. To that end, he hires private detective Major Raja Mannar (Kamal Haasan) to follow her when she goes on a European cruise for a vacation. Mannar accepts, as he desperately needs money to pay the hospital bills of his friend Rajan (Ramesh Arvind), who is afflicted with cancer, and his wife Mallika (Urvashi). Contrary to Madanagopal's suspicions, Ambujakshi is loyal and virtuous; when Mannar reports this, Madan refuses to pay him as his suspicions were unfounded.

Disappointed, Mannar to save his dying friend Rajan fabricates a story and tells Madan that she is having a secret affair during her trip. In the process, he introduces himself as a tourist to Ambu, her friend Deepa (Sangeetha) and Deepa's children, and becomes close to the group. while getting closer to Ambu, Mannar says to Madhan that Ambu is good but the other guy is bad, but madhan does not want to hear that and eventually breaks up with Ambu. While recollecting his past as an Army officer, he reveals that he lost his wife three years ago in a car accident. Ambujakshi realizes to her horror that the accident was caused by herself during an argument with Madan which was shown in initial part of the movie. Both of them decide to confront each other with the truth, but Ambu misunderstands Kurup (Manju Pillai) as Madhan's detective and slaps him and tells that she loves Mannar. Meanwhile Rajan should undergo an operation immediately after the chemotherapy to keep him alive. To make things worse Madan announces that he will visit them in person at Venice. Ultimately, Mannar and Deepa stage a plan with the help of Kurup to deceive Madhan for the final break-up with Ambu.

Madhavan arrives at the place and some mix-ups and misunderstandings take place among the characters. Madhavan realises that Ambu has fallen in love with Mannar and accepts it with a heavy heart. The film ends on a lighter note by showing Madhavan and Deepa