Malavath Poorna, daughter of a tribal farm labourer, said she reached the 8,848 metre peak on May 25 following a difficult and dangerous climb from the Tibetan side of the mountain in China.
Poorna said she and her 16-year-old friend, a member of India's lowest Dalit caste previously known as "untouchables", climbed the mountain with ten Nepalese guides before hoisting the Indian flag.
"I started to train for Everest last September, my parents and my instructors were very encouraging," Poorna told AFP in Kathmandu before heading home to India.
The 52-day-long expedition to Everest was made possible after an Indian government-run welfare group sponsored the teenager, whose father belongs to an indigenous tribe and earns just 600 USD a year.
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The petite schoolgirl said she was a confident climber and only felt nervous the day she made her final push to the summit.
"That morning, I saw six dead bodies on my way to the summit. My instructors had told me about climbers dying and their corpses being left on the mountain, but I was still shocked to see it," she said.
Kathmandu-based Jeevan Shrestha, who assists mountaineering expert Elizabeth Hawley, with the database said, "Poorna is the youngest female to summit Everest. It is a very rare achievement."
China and Nepal officials have not confirmed that she reached the summit.
Most climbers attempt the peak from the Nepalese side, the easiest and most popular route but authorities in Kathmandu do not grant climbing licences for Everest to anyone under 16.
The Indian teenager brushed off such concerns, saying, "I am glad I got the chance to climb. If I am fit enough, why should anyone stop me from climbing?"
She said she planned to join India's police force after finishing her education and climbing a few more peaks.