King Charles and Queen Camilla touch down in Australia

A 12-year-old boy is among the dignitaries to welcome King Charles III and Queen Camilla to Australia as the monarch kicks off a delicately planned, rapid royal tour.

The first visit by a reigning monarch in more than decade almost began in drenching rain, only to ease as the royal plane approached Sydney on Friday night.

Confidently descending from a RAAF jet, King Charles stepped onto Australian soil for the first time in six years with a grin, before being warmly greeted by his Australian representative, Governor-General Sam Mostyn.

Prime Minister Anthony Albanese and NSW Premier Chris Minns tucked away their republican beliefs, dipping their heads and heartily shaking the sovereign's hand.

The 75-year-old regent, who has paused cancer treatment to travel to Australia and Samoa, also shared a laugh with the prime minister's fiancee Jodie Haydon.

But the warmest reception was reserved for the youngest of the Australian contingent, as 12-year-old Ky got his wish to meet the royals.

The beaming boy, supported by the Make-a-Wish Foundation, offered a posy of waratahs to Queen Camilla and discussed the arrangement with Her Majesty, alongside his proud family.

The royal couple were soon whisked away in a police motorcade, through the city to a harbourside residence.

They are expected to rest on Saturday before official engagements begin on Sunday.

The trip is the couple's first Australian visit since the King ascended to the throne in 2022 and the first by a reigning monarch since Queen Elizabeth's 2011 tour.

But unlike that extensive 10-day trip by his mother, engagements and travel have been pared back considerably in light of the King's cancer diagnosis in February.

Still, the royals will be kept busy with formal dinners, wreath laying, fleet inspecting and hand-shaking during their five-day tour of Sydney and Canberra.

Members of the public will have multiple chances to glimpse Australia's new monarch at iconic sites including the Australian War Memorial, federal parliament and the Sydney Opera House.

The Opera House sails are being lit up for the couple's arrival on Friday night, albeit after a delay caused by the coincidentally named cruise ship, Queen Elizabeth.

The royal couple are expected to rest on Saturday to recover from their 24-hour journey.

The Australian Monarchist League's Damien De Pyle said it would be a privilege for the nation to welcome the King back to Australia.

"It's obviously a very special country for him ... this is the first Commonwealth country he's visited since becoming King," Mr De Pyle told AAP.

Official duties begin on Sunday, including a church service and a visit from Governor-General Sam Mostyn and NSW Governor Margaret Beazley.

But speculation is building that Royal Randwick could live up to its name and be graced with a discreet appearance from the couple on Saturday for the world's richest horse race outside the United Arab Emirates, the $20 million Everest.

The pair will travel to Canberra on Monday, where they will lay a wreath at the Australian War Memorial before receiving an official welcome at Parliament House.

The royals will also meet with Prime Minister Anthony Albanese and Opposition Leader Peter Dutton, plant a tree, and tour the botanic gardens.

Fans will be able to see the pair about midday at the For Our Country memorial, which commemorates the military service of Aboriginal and Torres Strait Islanders.

Sydneysiders will be able to see the King and Queen at the Opera House on Tuesday about 4.30pm.

Australian Monarchist League volunteers plan to hand out flags at the Opera House, while a small group of UK republicans plan to protest in Sydney and Canberra.

Forty per cent of Australians don't know the British monarch is also Australia's head of state, according to research commissioned by the Australian Republican Movement.

Mr Albanese floated a possible referendum for Australia to become a republic if his government was returned for a second term.

But the idea was shelved after the failed 2023 referendum to establish an Indigenous voice to federal parliament.

The royal couple will also visit the National Centre of Indigenous Excellence in Redfern and attend a community barbecue in Parramatta, before embarking on a review of the Royal Australian Navy fleet.

The King and Queen depart Australia on Wednesday morning for Samoa, where they will open the Commonwealth Heads of Government Meeting.

King Charles, who has paused cancer treatment during his travels, travelled to Australia 15 times before ascending to the throne.