Five men have been sentenced to death and one jailed for life over the 2007 murder of a couple who married against the wishes of village elders.
The court in the northern state of Haryana last week convicted the men of the murders of Manoj and Babli, who were killed a month after they eloped.
Elders said they violated local customs by marrying within the same sub-caste.
Observers say this may be the first time an Indian court has awarded such a penalty over an "honour killing" case.
The young couple were kidnapped while they were travelling on a bus in Haryana in 2007. Their bodies were discovered later.
Those sentenced to death are all relatives of the girl, Babli, and include her brother, two uncles and two cousins, Indian media reports say.
The head of the village council in Haryana's Kaithal district, which ruled against the couple's marriage, was given life imprisonment. A driver found to have helped abduct the couple was given a seven-year prison term.
The village council said that by local tradition people within the same sub-caste are considered to be siblings.
The case was brought by the family of Manoj, Babli's husband. Unconfirmed media reports say that the couple had approached the police with their fears shortly before they were kidnapped and killed.
Campaigners hailed the verdict as a blow against "honour killings", which are quite common in parts of northern India.
Correspondents say such killings have often not been reported or widely discussed in the past because families usually accept the verdicts.
Those found guilty in the case have the right to appeal. Death sentences in India are rarely handed down and even more rarely carried out.