The Fifth Reaction (Persian: واکنش پنجم) is an Iranian film which was made in 2003, written by Mehrnoosh Khorsand and directed by Tahmineh Milani. The main super stars are Niki Karimi, Jamshid Hashempur, Shahab Hosseini and Merila Zarei.

The film depicts Fereshteh's adversities, an underpaid school teacher, after she loses her husband in an accident, so her father-in-law takes the custody|custody]] of her two sons unless she marries his younger remaining son. Fereshteh makes up her mind, and decides to escape abroad by the aid of her friends, so she can take care of her sons; however, her father-in-law suspects and in a hot pursuit, throws her in jail.

The Fifth Reaction, released in 2003, reveals how the patriarchal society views women, and their cultural position. It is Tahmineh Milani's seventh movie regarding women's social position and rights in a patriarchal society which encourages women to struggle to get their human rights back. The movie reflects the inability of Iranian women to take any action in a patriarchal society, and its major concerns are female identity, women's position and power in the society, sexism, the social inequality and injustice, and mainly law's ignoring women's rights in child custody case. Tahmine Milani has related to these matters to awaken women and inspire them to fight for their rights. Fortunately, her works have a great impact on women's awareness and inspire them to try for their social improvement.