STX (Dalian) Shipbuilding has started operations at Changxing Island in Dalian, China.
The company, a subsidiary of the STX Group and the investor of the project, said the boatyard is now the largest in the world.
The yard can accommodate two 320,000dwt ships simultaneously.
At 460m long, the boatyard is 1m longer and 1m wider than the former largest Subic Shipyard in the Philippines, the company said.
The company has not revealed the cost of the yard.