Antha 7 Naatkal (read as "Antha Ezhu Naatkal") is a 1981 Tamil language film. Directed by and starred in by K. Bhagyaraj, the movie follows the life and ambitions of the hero, Palakkad Madhavan played by K. Bhagyaraj and his sidekick Gopi (child actor Khaja Sharif). The movie was a great hit and very well received by the public. It was remade in to the Telugu as Radha Kalyanam and then made in Hindi as Woh Saat Din.
The story starts off with Vasanthi (Ambika) and Dr. Anand's (Rajesh) marriage. On their wedding night Vasanthi attempts suicide and is saved by Dr. Anand. He then inquires about her past. Vasanthi tells him of her failed love affair with Palakkad Madhavan (Bhagyaraj). Palakkad Madhavan is a poor, naive, honest, aspiring music director with a huge family back home to support. His assistant Gopi is a kid wise beyond his age who has the knack of surviving in a big town. They move into an upper portion of the house where Vasanthi lives with her grandfather, mother, sister and a disabled brother. Initially Vasanthi sympathizes with Madhavan's unfortunate financial situation but eventually falls for his naive innocence and integrity in spite of his difficulties. Madhavan initially refuses Vasanthi's advances fearing her family and his financial inability to support her but eventually accepts her love.

While their love is blossoming, Vasanthi's parents get a proposal for Vasanthi from a wealthy widower who wants to marry a middle-class lady who would take care of his daughter and be a good daughter-in-law to his ailing mother. Vasanthi's grandfather and mother decide to marry her to the doctor. Vasanthi refuses the proposal and decides to get married to Madhavan at a temple the next day. Her family and other people from her neighbourhood injure Madhavan and force Vasanthi into a marriage with Dr. Anand. She explains to Dr. Anand that she is unable to change her heart and accept him as her husband.

Hearing of Vasanthi's past, Dr. Anand decides that she should reunite with her lover and he will help her do that. He asks her to stay in his house for a week as his terminally ill mother is counting her last days. Vasanthi agrees to this while Anand is looking for Madhavan in Kerala and in Madras. During her seven-day stay with Dr. Anand, she starts interacting with him, his mother, his daughter. When her husband finds and brings Madhavan to take Vasanthi with him, she refuses to go and decides to stay with her husband. The movie ends with Bhagyraj's famous line "my lover can become your wife but your wife can never become my lover. That is our culture".