Mr Fadanvis, who is 42, emerged as a consensus choice of the BJP's two Maharashtra factions led by former national president Nitin Gadkari and state-level strongman Gopinath Munde.
Mr Fadanvis is seen as close to neither group. He represents South West Nagpur in the state assembly and is known as a politician with a clean image.
"This is a huge responsibility. Our priorities will be those of the people of Maharashtra," he said.
Mr Fadanvis, a fierce critic of the ruling Congress-NCP, demanded that Maharashtra Deputy Chief Minister Ajit Pawar resign for making crass remarks against a farmer demanding water.
Mr Fadanvis, whose family is considered close to RSS leaders, joined politics early. At 21, he became the youngest corporator of the Nagpur Municipal Corporation. At 26, he was the youngest mayor of Nagpur. This is his third consecutive term as legislator.
Mr Fadanvis replaces the outgoing president, Sudhir Mungantiwar.