Hundreds queued up to be the first to enter what has been billed as the world's largest casino in Asia's largest building.
The Venetian Macao Resort Hotel cost $2.4bn (£1.2bn) to build and boasts 3,000 suites, some 16,000 staff, shopping arcades and a 15,000-seater sports arena.
The vast casino holds 870 gaming tables and 3,400 slot machines, with room to expand to 6,000.
Italian-style frescos adorn the walls and ceilings and a full-size replica of Venice's Bridge of Sighs greets visitors to the resort.
There is even an indoor canal - under a fake sky ceiling - on which sail Chinese-style sampans and Venetian gondolas.
The man behind the project, US billionaire Sheldon Adelson, inaugurated the resort by smashing a champagne bottle against a hotel gondola.
He said it had been his dream to "reproduce the capital of entertainment in Asia for Asians".
Mr Adelson and his Las Vegas Corp group have helped transform Macau into a lucrative gambling hub.
Last year, gaming revenues in the small Chinese territory totalled $7.2bn (£3.5bn), overtaking the Las Vegas Strip for the first time.
But correspondents say the pace and scale of change in Macau has led to a labour shortage, environmental damage and a growing gap between rich and poor.