The flag will be raised at English Heritage sites in the region on Monday to mark Commonwealth Day.
Warkworth and Berwick castles, Belsay Hall, Corbridge Roman Town and Tynemouth Priory are all taking part in the Fly a Flag for the Commonwealth initiative.
Around the world, more than 950 Commonwealth flags will be raised at 10am local time.
A wide range of groups and organisations will be taking part, including local authorities; school children; Guides; Scouts; Sea, Army and Air Cadets; Commonwealth ex-servicemen; P&O and Cunard Line; and the Jubilee Sailing Trust.
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Now in its third year, the event allows participants to show their appreciation for the values the Commonwealth upholds and the opportunities offered for friendship and cooperation with fellow Commonwealth citizens around the world.
Simon Bean, English Heritage’s historic properties director for the north, said: “We are very pleased to be involved with the Fly a Flag for the Commonwealth initiative.
“Our castles and historic properties tend to be set in very prominent positions, so those in the local area of properties taking part will be able to spot the Commonwealth flag flying high on March 13.”
English Heritage properties across the country will be taking part, from Berwick in the north to Kent in the south.