Mechery Louis Ouseppachan (born 13 September 1955), known mononymously as Ouseppachan, is an Indian film composer and singer who primarily works in Malayalam films. He is a recipient of one National Film Award and three Kerala State Film Awards for his numerous film soundtrack albums and background scores.

Ouseppachan was born to Mathiri Paliakkara and Louis of the Mechery house on 13 September 1955 in Ollur, Thrissur, Kerala, India. He started his music career as violinist in some music troupes including Voice of Trichur. Later he got the chance to be the violinist in concerts of renowned playback singer Madhuri. He later became the violinist under music director Paravoor Devarajan master.[2] His first work in the film industry was the film Eenam, for which he set the background score. He also composed additional background music for the film Aaravam (1979) in which he also played the role of a fiddle player, however Kathodu Kathoram (1985), directed by Bharathan is considered as his debut. Ouseppachan's work was noted for the film and three songs from the film became super hits. These songs were noted also for the immense use of violin. This may be attributed to the facts that Ousephachan himself is a violinist and that the protagonist of the film played by Mammootty is also a violinist. Ousephachan then went on to compose music for over 120 films. He also composed songs for the non-commercial Hindi film Freaky Chakra, directed by V.K. Prakash and background scores for various other Hindi films, notably directed by Priyadarshan.