Unofficial world record: RSPCA sheep's massive fleece the heaviest in the world

The shearing operation that potentially saved the life of an errant sheep with a mammoth fleece found near Canberra this week has also set an unofficial world record.

The wool shorn off Chris the sheep officially weighed in at 40.45 kilograms after the weight of the bag was removed, according to RSPCA ACT - more than 10 kilograms heavier than the existing record-winning fleece.

The overgrown sheep was found near Mulligan's Flat on Wednesday and dubbed Chris by the person who found it.

New Zealand's Big Ben has held the Guinness World Record for the most wool sheared from a single sheep since January 25, 2014 with 28.9 kilograms removed.

Big Ben's record is closely followed by a fellow Kiwi sheep dubbed "Shrek".

Shrek avoided musterers for six years before finding fame back in 2004 when he was discovered in a cave with 27 kilograms of unshorn wool.

The RSPCA estimated Chris the sheep had "five years of wool on him" and said he "could barely walk" prior to his haircut.

Shearer Ian Elkins took about 45 minutes to shed the 47cm-long fleece, which came off in one piece.

"Just the sheer volume and actually getting into the fleece was quite a challenge," he said.

"There was five of us [shearing the sheep] - everyone held a leg or a shoulder."

He said in 35 years of shearing he'd never come across a sheep like it.

"Occasionally we get a sheep that's gone over two years with a fleece without a shear and that's a bit of a challenge.

"A double fleece would probably only weigh about 10 or 12 kilos. The average fleece in Australia would cut five kilos. That this has cut over 40 kilos is quite amazing."

RSPCA ACT spokeswoman Jane Gregor said the sheep was in good condition and seemed to be recovering well.

"The sheep itself actually started walking towards the shearing equipment. I think it was going, 'Get this thing off me'," she said.

"He's one very lucky sheep."