Congress Party politician Shashi Tharoor, 62, has been charged over the death of his wife Sunanda Pushkar.
He has been accused of cruelty and for abetting her suicide in a five-star hotel room in 2014, according to a report by AFP.
Delhi police said they have amassed enough forensic and other evidence to pursue Tharoor in court.
The cause of Pushkar's death was listed as suicide – something Tharoor has long rejected. "No one who knew Sunanda believes she would ever have committed suicide, let alone abetment on my part," he said on Twitter.
Tharoor questioned the "methods and motivations" of Delhi police, suggesting a political vendetta was at play. He has denied any involvement in his late wife's death. The politician also called the charges "preposterous" and vowed to fight "vigorously" against the allegations.
In 2014, Pushkar was found dead two days after she publicly accused Tharoor of having an affair with a Pakistani journalist Mehr Tarar. At that point of time, Tharoor was an under-secretary-general to Kofi Annan at the UN.
Early autopsy results suggested that Pushkar may have overdosed on antidepressants and sleeping pills. Subsequent medical reports led investigators to treat the case as a murder. However, no suspects were named.