Before Sunil, Pappu Yadav had won the 48kg Greco-Roman title in 1993.
Sunil with his comprehensive defence, was able to keep Salidinov at bay for most part of the bout. Salidinov did not have any answer to the Indian's strategy and finally went down pretty easily.
Earlier, Sunil made an impressive comeback in his semi-final bout to reach the final. He was down 1-8 against his Kazakh opponent Azamat Kustubayev but made a great comeback, grabbing 11 points on the trot to win the bout 12-8.
In 2019 also, Kumar had made it to the final and ended with a silver medal.
"I am feeling happy to have earned India's first gold medal today. I have worked really hard on my ground techniques and it feels good to have done better than my last year's performance," Sunil said later.
Before Sunil's historic gold medal, Arjun Halakurki (55kg) won a bronze by defeating Donghyeok Won of Korea 7-4.
Arjun started the bout slowly and was down 1-4 in the first period. But, the Indian did not give up and came back strongly, snatching six straight points with a combination of good defence and attack.
Arjun lost his semi-final bout against Iran's Pouya Mohammad Naserpour earlier in the day.
India's third medal hope Mehar Singh (130kg), however, narrowly lost his bronze medal bout against Roman Kim of Kyrgyzstan 2-3. Mehar was feeling the after effects of his wrist injury which he suffered in his semifinal bout.
In the semifinals, Mehar went down 1-9 to Minseok Kim of Korea.
Mehar had made the Indian team at the last minute. Just three days before the tournament, India's number one in 130 kg, Naveen, pulled out of the event due to injury.
Mehar replaced Naveen and won his opening bout against Daler Rakhmatov of Uzbekistan.
In the first qualification bout of the day, Sajan, who was one of India's big medal hopes lost in a disappointing manner.
He was pitted against under-23 Asian champion Renat Iliazuulu of Kyrgyzstan in the first round. The Indian wrestler could not match the initial onslaught of Iliazuulu and lost 6-9.
Sachin Rana (63kg) faced a massive defeat against Elmurat Tasmuradov by a margin of 8-0.
He was then pitted against Yernur Fidakhmetov of Kazakhstan where he could not put up much of a challenge and went down 6-3 in his Repechage bout.