Vallavan (transl. Expert), alternatively spelled as Valaavaan, is a 2006 Indian Tamil-language romantic thriller film written and directed by Silambarasan, starring himself in the lead role alongside Nayanthara and Reema Sen whilst Sandhya, Santhanam, Premji and Sathyan play supporting roles. The dialogues are written by Balakumaran, and the film was produced by P. L. Thenappan. The film's score and soundtrack are composed by Yuvan Shankar Raja. The story follows Vallavan, a happy-go-lucky college student who falls in love with Swapna. He soon discovers that Swapna is a trainee lecturer at his college and is three years older than him.

Vallavan released on 21 October 2006. It received mixed reviews and became a decent hit at the box office. The songs became chartbusters.

Vallavan is a happy-go-lucky college student. While he and his friends are at a temple, he sees Swapna and immediately falls in love with her. Vallavan reencounters her, and she is revealed to be a lecturer who is three years older than him. He decides to woo her by turning into Pallan, an ugly duckling with buck teeth and thick glasses. Pallan makes Swapna fall in love with him for his heart. He then reveals his disguise at a wedding reception and introduces her to his friends. At the party, they try to convince her indirectly to accept a younger man, but she doesn't budge. After that, Vallavan drops her off at her home. Both feel romance and make love. He assures marrying her. When Swapna learns that Pallan is younger than her (from one of Vallavan's rivals at the college) and also a student, she breaks off her relationship with him and decides to marry another man.

As Vallavan walks in the streets, wondering how things got so messy, he recalls his school life. When he was in higher secondary school, Vallavan met the hysteric and toxic Geetha, who ensures that Vallavan is mad about her. Learning of her true nature, he ends their relationship. She is not ready to let him go so easily, and he teaches her a lesson.

Geetha returns for payback and tells Vallavan that she is the reason for the current mess in his life. In an effort to win his love, Vallavan, once again as Pallan, goes to convince Swapna that even though he is younger than her, his love for her is true, and age does not matter. Swapna realizes her mistake, and they reconcile, infuriating Geetha. In a climax displaying her disorder, she kidnaps Vallavan's friend Suji, and Vallavan arrives and frees her.

The film fast-forwards to three years later, where Geetha is released from a mental asylum. The moment she steps out, she exhibits her fiery, psychotic expression, showing that she never actually recovered. Vallavan is waiting for her, and they communicate telepathetically, with Vallavan saying that she cannot hurt him.

The music was scored by noted musician and Silambarasan's friend, Yuvan Shankar Raja, coming together again after churning out the successful album of Manmadhan (2004). The soundtrack was released on 1 June 2006 and features nine tracks, including seven songs and two instrumental pieces. As it was the case in Manmadhan, a second soundtrack was released afterwards with bit songs that feature in the film but not on the first soundtrack along with pieces from the film score. The lyrics were penned by Vaali, Thamarai, film director Perarasu and Silambarasan himself. Karunakaran wrote the lyrics of the bit song "Kadhal Vandhale", released in the second edition.

Yuvan Shankar Raja won accolades for his soundtrack, whereas especially the songs "Loosu Penne" and "Yammaadi Aathaadi" were both popular. The song "Kadhal Vanthirichu" was remixed from the film Kalyanaraman (1979), composed by Yuvan's father Ilaiyaraaja.