The Kurmi leader lost from Bareilly in 2009.
He was the chief whip of BJP in 14th Lok Sabha.
This time he has won from Bareilly by a margin of over two lakh votes.
Mr Gangwar, who has been associated with social work and active politics for over three decades, was jailed during the Emergency.
He earlier held ministerial posts at the Centre as Minister of State for Petroleum and Natural Gas with additional charge of Parliament Affairs.
He was also Minister of State of Science and Technology.
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