It wouldn't beat out the 450 gram world record holder, but Wendy Larkin's oversized chicken egg might be the biggest in Nelson.

Larkin, 75, found the 9 cm long egg last week on her Vanguard Street property where she keeps a dozen Ross Brown hens.

She said it's the largest she's ever seen, and an unusual offering from her brood.

"It's more than double the size of anything else my hens have laid.

"I've got good size eggs, but you would only get a double-yolker every three months or so," Larkin said.

Some have suggested the egg might be a triple-yolker, but Larkin is yet to crack the mystery.

She often sells her chickens' eggs privately or gives them to the Nelson Hospital chaplaincy, but is unsure what to do with the monster egg.

"I don't think it would taste very good," she said.

Friends have expressed sympathy for the egg's parent.

"Always the women are saying 'oh, that poor hen.' It's a bit like a mum having a big baby."

Larkin doesn't know which of her hens is responsible, but will be looking out for the one hen known to lay eggs of a similar pale hue.

Ultimately, she thinks the freak egg is "just a fluke" and expects more regular lays in the future.