Sydney Harbour will host a new multi-million-dollar floating opera from March 2012.

The platform is to be moored off the Royal Botanic Gardens and, over a six-week season, there will be a total of 22 performances by Opera Australia, with more than 60,000 tickets on offer.

The first performance will be Verdi's La Traviata and is set to feature a giant chandelier and fireworks.

"The grandeur and majestic beauty of Sydney Harbour is the perfect backdrop for this spectacular opera," NSW Premier Kristina Keneally said.

"A ticket to Opera On Sydney Harbour will provide a once-in-a-lifetime experience in one of the most beautiful cities in the world," she added.

Supported by the NSW Government through Events NSW, Opera On Sydney Harbour is planned to be staged annually.

The revenue from the event is set to bring more than $20 million to the state every year.

"This event will entice visitors to Sydney, as Opera On Sydney Harbour joins the list of prestigious outdoor opera events, including Aida At The Luxor, Turandot In The Forbidden City and Opera At Lake Constance in Bregenz, Austria," Ms Keneally said.

- ABC/AAP