Hundreds of rainbow flags were on display across the city in wide-ranging support for the cause, while many landmark buildings were lit up in the familiar rainbow hues on Saturday night.

Despite poor weather forecasts and police concerns over possible terror threats, up to 300,000 people were thought to have taken part in celebrations that lasted long into the night.

Dykes on Bikes - one of Australia's oldest LGBTQI groups - kicked off the celebrations, followed by thousands of other feathered and fleshy marchers.

"We all want equal rights. We all deserve it too," one parade-goer told the SBS.

More than 1000 New South Wales Police officers were out in force, after announcing extra security provisions in response to recent international incidents targeting LGTBQI community events, including the Orlando gay nightclub massacre.

The buzz surrounding the world-famous event bubbled over in the days leading up. Sydney Airport was vibrant with anticipation; one highlight was the attendance of the 'Sistagirls' from the Northern Territory's Tiwi Islands.

The group of 30 Indigenous transgender women travelled to the festival for the first time to share their story of resilience and finally acceptance in their community, following a mass fundraising effort.

Sydney Queer Irish brought another distant piece to the puzzle of inclusion and having joined more than 12,000 entrants and about 180 floats in this year's parade.

Prominent voices in the LGBTQI community added to the hype surrounding this year's event, including Ian Roberts, who led the National Rugby League float decades after coming out - the first professional of any football code to do so while playing.

Social media too was alight as #mardigras2017 went viral, while businesses and groups alike shared altered versions of their logos to incorporate the rainbow.

Just one of many public service organisation to get in on the fun, Sydney Trains had rainbow flags on display in multiple stations, while volunteers from the RFS also made their feelings known through stunning one-off epaulets.

Equality had always been central to the philosophy of Mardi Gras but its message also went beyond marriage equality, said Mardi Gras chief executive Terese Casu.

Malcolm Turnbull, who became the first sitting prime minister to attend the celebrations last year, wasn't at the parade.

However, he says he remains a strong supporter of the event.

"I go most years," he told reporters in Queensland.

NSW Ambulance deputy commander Wayne McKenna said before the event a strong contingent of paramedics would be on hand but warned revellers to think about safety.

smh.com.au, with AAP