The sick fin whale, stranded against a harbour wall in Baltimore in west Cork since Tuesday, has now died.
The 46ft whale had attracted attention over the past few days after it resisted attempts by fishermen to coax it back into open waters.
Pádraig Whooley of the Irish Whale and Dolphin Group says it's great the whale's suffering has ended.
"Whales, when they get themselves into situations like this, just don't survive. They get stranded if they're sick and in poor condition.
"There are very few documented cases from anywhere around the globe of whales miraculously turning these situations around and swimming out to open water and having a 'Free Willy' moment. These are works of fiction."