Indian law prohibits naming the woman victim, a trainee physiotherapist from a lower-middle class family who had worked in a call center, but Indian media have dubbed her Nirbhaya, a Hindi word meaning fearless.
The verdict capped a seven-month trial, often held behind closed doors, that was punctuated dramatically by a fifth defendant hanging himself in his jail cell. Outside the court, the case cemented India's reputation as unsafe for women, even after parliament passed new laws against sexual crimes.
(Read more: Accused in Delhi gang rape hangs himself in jail)
Nirbhaya's case resonated with thousands of urban Indians who took to the streets in fury after the attack. Her path through education onto the first rungs of middle-class life seemed to epitomize the aspirations of millions of young women in the world's second most populous nation.
Bus cleaner Akshay Kumar Singh, gym instructor Vinay Sharma, fruit-seller Pawan Gupta, and unemployed Mukesh Singh were found guilty of luring the woman and a male friend onto the bus on the night of Dec. 16 as the pair returned home from watching a movie at a shopping mall in south Delhi.
(Read more: Rape of 5-year old in India sparks protests)
As the bus drove through the streets of the capital, the men repeatedly raped and tortured the 23-year-old with a metal bar before dumping her and her friend, naked and semi-conscious, on the road. She died in a Singapore hospital two weeks later of internal injuries.