It's understood the royals landed at Sydney Airport a short time ago on a Qantas flight from London, not an earlier British Airways flight as had been previously reported.
Prince Harry and Meghan will then catch a ferry to the Opera House to watch a rehearsal by the Bangarra Dance Company and then take part in a royal walkabout to chat with "members of the public", later returning to the Governor-General's house for a "reception".
Harry and Meghan's tour of Australia officially begins tomorrow, however, they are spending Monday free from any engagements to recover from the jetlag of their 22-hour flight.
Their 16-day official royal tour will also include visits to Fiji, Tonga and New Zealand.
The tour coincides with the Invictus Games in Sydney, which run from October 20 to October 28.
Kensington Palace said: "There is a long history of friendship between the Royal Family and Australia, Fiji, Tonga and New Zealand, and their links with the United Kingdom are extensive".
The Duke and Duchess of Cambridge - Harry's brother and sister-in-law - came to Australia and New Zealand with a young Prince George in 2014 for an 18-day visit. They will also be joined by representatives from the Invictus Games, before heading to Taronga Zoo to become antiquated with two baby koalas.
After landing in Sydney, the duke and duchess will travel to Dubbo and Melbourne, before spending three days in Sydney from October 19-21 to mark the launch of the games.