It is designed to be a 182m (600ft) high tribute to Sardar Vallabhbhai Patel, a hero in India's independence struggle, in Gujarat state.
The Spring Temple Buddha in China is currently the world's biggest statue at 128 metres.
India's statue has cost 29.9bn rupees (£330m; $430m) and is seen as a pet project of Indian Prime Minister Narendra Modi.
The "Statue of Unity", as it is known, will be inaugurated by the Indian leader on 31 October.
Many Hindu nationalists feel his place in history was overlooked in favour of the Nehru dynasty, which came to dominate Indian politics.
While campaigning to becoming India's prime minister in 2013, Mr Modi said "Every Indian regrets Sardar Patel did not become the first prime minister".
Once completed, the bronze-clad statue - which was begun in 2013 - will be nearly twice as tall as New York's Statue of Liberty.
It is hoped the site will become a significant tourist attraction for the country's westernmost state.
