It will be led by Chris Tabraham, who retired from Historic Scotland in 2010 after 40 year’s service.
He spent most of his career in the Ancient Monuments Inspectorate, before retiring as principal historian.
During his career, he did much research on Scotland’s castles, including directing major excavations at Threave Castle in the 1970s.
He has also published extensively, his books including Scotland’s Castles and The Illustrated History of Scotland.
Claire Williamson, Cay You Dig It senior archaeologist, said: "Castles inspire a strange fascination but, in truth, their history is often far more eventful than anything we could think up.
"Castles are iconic in Scotland, but do we really know everything there is to know about these towering structures?
"Join us on May 11 and discover that there are still a few surprises up Galloway’s historical sleeve.”
The talk will take place via Zoom at 7.30pm, to book your free ticket visit www.eventbrite.co.uk/e/castles-of-galloway-latest-thoughts-tickets-327248768877
Galloway Glens education and community engagement officer, Jan Hogarth, added: “I can’t wait for this talk, I was fascinated in castles as a child always stunned by their presence and beauty in the landscape.
"Chris will bring to life for us how they were used and their relationship to the community around them.”