Gunaa is a 1991 Indian Tamil-language psychological romantic drama film directed by Santhana Bharathi and co-written by Sab John. The film stars Kamal Haasan, Rekha and newcomer Roshini (in her only film apperance). The story revolves Gunaa (Haasan) who kidnaps an heiress Rohini to make her fall in love with him. He believes she is an avatar of goddess Abhirami and it is his destiny to marry her.

Haasan and John initially planned to make a film set in Sri Lanka during a time of insurgency, but the project was dropped over story concerns. John later developed the story of Gunaa, inspired partly by a mentally-ill person he knew. The dialogues were written by Balakumaran, cinematography was handled by Venu and editing by B. Lenin and V. T. Vijayan. The film was mostly shot around Kodaikanal, including a cave then known as Devil's Kitchen.

Gunaa was released on 5 November 1991, Diwali day. It was critically acclaimed for its unique theme and performances, but had an average run at the box office. The film won a Tamil Nadu State Film Award, a Filmfare Award, and two Cinema Express Awards. It acquired cult status in Tamil cinema and inspired more films about mentally obsessed lovers, while Devil's Kitchen became a popular tourist spot after the film's release and later known as Guna Caves.

Gunaa is an asylum inmate. His cellmate tells him a story, whose protagonist Abhirami gets registered in Gunaa's mind; he believes and dreams that she is an avatar of goddess Abhirami who would marry him on a full moon day. After his psychiatric test, his psychiatrist Ganesh sanctions his release, but Gunaa keeps searching for Abhirami. His mother Manonmani runs a brothel after his father deserted her. Her brother-in-law, addressed as "Chitappa", is her aide. Rosy, one of the brothel girls, loves and desires to marry Gunaa, but he does not reciprocate.

Gunaa is an expert at breaking open locks, and Chitappa regularly takes his assistance for stealing. Chitappa decides to break open a hundi at a nearby temple to pay Manonmani's overdue rent. When he takes Gunaa for a rehearsal, Gunaa spots a wealthy heiress in the temple. Since her physical attributes match those of Abhirami as imagined by Gunaa, he approaches her and she smilingly gives him some sweets; her pleasant disposition convinces him that she is Abhirami.

On the scheduled day of heist, Chitappa, Gunaa and their men arrive at the temple. Gunaa opens the lock of the safe room and lets Chitappa's men inside. Seeing the heiress again, he goes after her, accidentally locking Chitappa's men inside. They are caught by officials but manage to escape with some jewels and flee with Gunaa via car. One of them dies when the car crashes, the wounded survivor seizes the heiress's car and starts driving it, with Gunaa also joining.

The wounded man succumbs, and the car falls into the sea. Ramaiah, a CBI officer, investigates the heiress's disappearance, and informs her guardian Suresh Kumar (SK). Having saved the heiress and the jewels from drowning, Gunaa takes them to his house. Landlord Ismail sees the financial reward in a newspaper for the safe return of the heiress. His goons assume her to be a new prostitute brought in without paying their usual bribe and fight with Gunaa. To save her, Gunaa drives her to a dilapidated church on a hilltop, and keeps addressing her as "Abhirami".

The heiress hates Gunaa for his weird nature and tries to escape, but fails every time. With Chitappa's help, SK and Ismail reach the church; SK coerces the heiress, whose real name is Rohini, to sign blank papers so he can control all her wealth. She assents to avoid being killed, but SK tries to kill her anyway. Gunaa intervenes, kills Ismail, knocks SK out and takes the injured Rohini to a cave for safety. Though she first hated Gunaa, she now understands his deep love. She reveals her real name, but prefers the name Abhirami and accepts Gunaa's marriage proposal. Though Gunaa is adamant on marrying on a full moon day, Rohini convinces him it is that day and marries him.