Vinay Sharma, one of the four convicts sentenced to death for gang-rape, torture and killing of a young medical student in December 2012, allegedly tried to commit suicide by hanging with a towel at Tihar Jail in Delhi on Wednesday.
The convict, whose condition is not immediately known, has been admitted to a hospital in Delhi.
Sharma, according to media reports, took pills before trying to hang himself.
Earlier, he had demanded more security in jail alleging that he was being beaten up by other inmates.
In 2013, Ram Singh, driver of the bus in which the 23-year-old paramedical student was assaulted and raped, had also committed suicide in Tihar Jail by hanging himself.
On December 16, 2012, the victim was fatally assaulted and gangraped by six persons in a moving bus in south Delhi and thrown out of the vehicle on that night. She succumbed to injuries in a Singapore hospital on December 29.