Several organisations were involved in a large scale search for the diver, who was last seen surfacing just after 11am today (Sunday) while diving near the Farne Islands.
Lifeboats from Seahouses, Craster and Berwick were all dispatched as well as a rescue helicopter.
Police and other coastal teams carried out a search from the land, with other vessels in the area also getting involved.
The diver was found at 2.30pm but despite being given medical attention, she died a short time later.
A police spokesman said: “At 1.50pm on Sunday April 3, Police received a report of a missing diver off the coast of Northumberland.
“A woman who was diving just off the coast of the Farne Islands went missing at approximately 11am this morning.
“The Coastguard launched a search of the area and at 2.30pm the diver was located, she received medical attention at the scene but unfortunately passed away a short time later.”