Their Majesties will attend a community barbecue in Sydney's west hosted by NSW Premier Chris Minns ahead of a meet and greet with well-wishers in front of the Sydney Opera House on Tuesday afternoon.
The last time a sovereign met the crowds at the Opera House was when the late Queen Elizabeth II visited in 2006.
Their Majesties will then participate in a Royal Australian Navy Fleet Review of five ships on Sydney Harbour.
The Navy, the Australian Army, and the Royal Australian Air Force will conduct fly-pasts and more than 600 officers and sailors will conduct a 'cheer ship' salute.
While in Canberra, King Charles was given a demonstration on how quickly a bushfire can burn. (Tracey Nearmy/AAP PHOTOS)
In the morning, the King and Queen will split up for separate engagements.
King Charles will visit the National Centre of Indigenous Excellence while Queen Camilla will visit Refettorio OzHarvest and Green Square Library in the inner city.
Later, the King will visit the Melanoma Institute where he will meet joint Australians of the Year Georgina Long and Richard Scolyer.
The King, 75, was earlier this year diagnosed with a form of cancer, the type of which has not been officially confirmed.
The final day of events for the royal couple comes after Victorian Senator Lidia Thorpe interrupted a reception in Parliament House on Monday to protest the monarchy.
"You are not our king. You are not sovereign," the Indigenous senator said before being led away by officials.
"You committed genocide against our people. Give us our land back. Give us what you stole from us - our bones, our skulls, our babies, our people," she said before being removed.
Anthony Albanese hosted King Charles at Parliament House in Canberra on Monday. (Saeed Khan/AAP PHOTOS)
While in Canberra, the King also laid a wreath at the Australian War Memorial and planted a gum tree at the Botanic Gardens.
He met with volunteer firefighters and researchers at the CSIRO bushfire behaviour lab, witnessing a demonstration of how quickly bushfires can spread and learning about suppression methods.
The Queen attended a roundtable discussion about domestic and family violence while the King met with Prime Minister Anthony Albanese and Opposition Leader Peter Dutton.
Following events in Sydney, the King and Queen travel to Samoa to open the annual Commonwealth Heads of Government Meeting.
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