The Night Manager star will replace Emma Corrin in the role of series five and six.
In a statement posted on the official Twitter page of The crown, the Australian actress said: ” Princess Diana ‘s spirit, his words and actions live on in the hearts of so many people.
“It is my real privilege and my honor to join this masterful series which made me absolutely addicted from the first episode. ”
Debicki is best known for her role as Jed Marshall in the 2016 BBC drama The Night Manager.
The 29-year-old also appeared with Leonardo DiCaprio in The Great Gatsby, the Sir Steve McQueen Widows movie and Marvel’s Guardians of the Galaxy Vol. 2.
She will next be seen in Christopher Nolan’s highly anticipated new film Tenet, which is set to be the biggest release since UK cinemas reopened after the lockdown when it hits the big screen later this month.
Earlier this week it was announced that Jonathan Pryce to succeed Tobias Menzies play the Duke of Edinburgh for the last two series of the big budget show.
The 73-year-old admitted taking on the role was a “daunting prospect.”
Imelda Staunton has already been named the next Queen and Lesley Manville as Princess Margaret.
They will replace Olivia Colman and Helena Bonham Carter respectively, who will retire after the upcoming fourth round.
The fifth and sixth series will bring the monarch’s reign into the early 21st century, but before that they could face several royal crises, including Prince charlesis separated from Diana – part of the Queen’s ‘annus horribilis’ from 1992.
This year also saw Prince Andrew separated from Sarah, Duchess of York, from the burning of Windsor Castle and Princess Anne’s divorce from Captain Mark Phillips.
Other episodes will likely deal with Diana’s death in 1997 and those of Princess Margaret and the Queen Mother a few weeks apart in early 2002.
The fourth series of the royal Netflix drama stars X-Files star Gillian Anderson as Margaret Thatcher and will be released later this year.