A 20-metre male fin whale died a few hours after it was found washed up on a beach in Achill Island.
The mammal was alive on stranding but died a few hours later, according to local RNLI officers.
A steady stream of people went out to see the fin whale on Keel beach in Achill Island today, according to the Irish Whale and Dolphin Group.
The group's chairperson Willie Meuhlausen travelled up to take samples including skin, blubber, muscle and baleen as well as photographs.
The group's stranding officer Mick O'Connell said it was most likely in poor condition when it was beached on Christmas Eve.
"It came in alive on Christmas Eve, and it died a short time later. There's absolutely nothing we can do; it's 17 metres long. Once it washes up unfortunately that's it."
Mr O'Connell said strandings are unfortunately painful for whales.
"If a whale is in the water, it doesn't feel its own weight. But when they get washed up on land, they're more or less crushed by their own weight."
While whale strandings are uncommon in Ireland, the IWDG is warning that this will change because the population of fin whales is increasing in Atlantic waters because of conservation.
The fin whale in Achill will remain on the beach over the next few days and the group has welcomed visitors to come and see the mammal.
IWDG said although the whale is dead it is "still a fantastic opportunity" to see the second largest animal on the planet.
However, it asked visitors to respect the carcass.