The body of what is believed to be a large fin whale has washed up on the Mizen peninsula in west Cork.
The discovery was made in the Barleycove area yesterday.
Stephanie Levesque, of the Irish Whale and Dolphin Group (IWDG), said the body was in poor condition when it was discovered.
"It's very decomposed and there are large shark teeth evident on the carcass," she said.
The group is cautioning the public against approaching the whale.
"Dead animals always represent a health risk so we would advise people not to get too close to it," she said.
It is not clear what caused the whale's death.
Fin whales are the second-largest mammal in the world and can grow up to 25m long.
They have a typical lifespan of between 80 to 90 years.
Speaking on RTÉ's Morning Ireland, marine biologist Jasmine Stavenow Jerremalm, who volunteers with the IWDG, said one or two fin whales wash up on Irish beaches each year.
"When we went out to it three days ago, it had already been dead for several weeks approximately.
"It [came] ashore three days ago and we went out to it and we could see that it was a female fin whale and we measured it to 17.5 metres. So, a very large whale," Ms Stavenow Jerremalm said.
She also urged the public to stay away from the carcass because they cannot determine why the whale died.
"To do that, you need our proper post-mortem scheme with veterinary pathologists looking into the cause of death.
"But we can definitely say which species it was and we could collect samples which are important for future research projects," Ms Stavenow Jerremalm said.
