In Harihar Nagar is a 1990 Indian Malayalam-language comedy thriller film written and directed by Siddique-Lal. The film, set in the fictional locality of Harihar Nagar follows four unemployed bachelors: Mahadevan (Mukesh), Appukuttan (Jagadeesh), Govindan Kutty (Siddique) and Thomas Kutty (Ashokan) and their attempts to woo their new neighbour Maya (Geetha Vijayan), who is in town to investigate the mysterious circumstances surrounding the death of her brother. It also stars Rizabawa, Kaviyoor Ponnamma and Rekha, with Suresh Gopi and Sai Kumar making cameo appearances. The music was composed by S. Balakrishnan.

In Harihar Nagar was released on 8 November 1990. The film was the fourth highest grossing Malayalam film of the year and ran for more than 100 days in theatres. The film is widely celebrated as one of the most popular Malayalam comedy films ever and has over the years gained a cult following, spawning two sequels — 2009's 2 Harihar Nagar, and 2010's In Ghost House Inn — and remakes in Hindi (Parda Hai Parda and Dhol), Kannada (Nagaradalli Nayakaru), Tamil (MGR Nagaril), and Telugu (Madhura Nagarilo). Its success also spawned a series of unrelated low budget comedy films featuring the principal cast, in the years that followed.