There were cheers outside the court as gym instructor Vinay Sharma, bus cleaner Akshay Kumar Singh, fruit-seller Pawan Gupta and unemployed Mukesh Singh were sentenced to be hanged.
"These are the times when gruesome crimes against women have become rampant, and courts cannot turn a blind eye to the need to send a strong deterrent message to the perpetrators of such crimes," Judge Yogesh Khanna said.
Today's sentencing caps off a seven-month trial that has become a notorious symbol of the high rates of violent sex crime against women in India.
ITV News correspondent Nina Nannar reports:
The 23-year-old victim was lured onto a bus with her male friend in Delhi last December.
The pair were then attacked by a group of men who beat up her companion and raped and tortured the woman with an iron bar for an hour. The bus was driven around the capital as the attack was taking place.
Both were later dumped by the side of the road. The woman died of her injuries two weeks later.
A fifth defendant hanged himself in his cell during the course of the trial, while a sixth received a three-year prison sentence - the maximum possible for juvenile offenders.
Relatives of the victim, who have spoken to the media as the trial unfolded, said they were pleased with the sentence.
"Today we can breathe a little easier," said her mother, who hugged a police officer outside the court after the sentence was read.
Her younger brother, Gaurav Singh, told ITV News he was pleased the four men had been sentenced to death. "That is what they deserve and they should be hanged," he added.
Lawyers for all four men said they would appeal, which means their execution could still be years away.
The case will go to the High Court and then Supreme Court. If they confirm the sentences, the final decision will lie with the president, who has the power to grant clemency.
Indian courts sentenced some 1,455 prisoners to death between 2001 and 2011, but only three people have been executed in the past 17 years. There are currently 477 people on death row.
This case has inflamed public debate about sexual crime in India and provoked hundreds of demonstrations across the country. It also led to the introduction of tougher rape laws in March.