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 shearer who is undergoing a potentially life-saving shearing operation to save a very woolly sheep found near Canberra believes he has set a new record.

The errant sheep who appeared wearing a mammoth fleece began undergoing a risky shearing operation from 9am in the hopes of saving its life.

Shearer Ian Elkin took about 45 minutes to finish the first pass and estimated that the fleece weighed about 42.5kg.

A New Zealand sheep which had avoided musterers for six years found fame in 2004 when it was discovered in a cave with 27 kilograms of unshorn wool.

Dubbed "Shrek" after the fairytale character, New Zealand's most famous sheep was eventually shorn with the proceeds going to charity.

Mr Elkin said he "smashed Shrek's record of 27kg no worries".

"I don't think he's been shorn before, and I think he's five or six years old," he told local radio.

"I wouldn't say it is high quality, but you wouldn't expect it to be after so long in the bush."

He said he had to do it in two layers, and he took about 45 minutes to finish the first pass. The sheep will be checked by vets, but initial indications were it came through the process relatively well.

The RSPCA estimates the sheep has "five years of wool on him" and it "could barely walk".

The sheep was found by a member of the public near Mulligan's Flat and rescued by a team of five from the local RSPCA and was being sheared by a shearer, his son and a helper, according to reports.

The team put out an urgent call for a shearer.

Apparently the RSPCA even had media requests from Polish news about the woolly animal.

Ian Elkin, the shearer, has shorn before royalty at the Royal Sydney Show.

The sheep had never been near humans for several years at least, by some estimates. And RSPCA ACT boss Tammy Ven Dange has warned the process of shearing could lead to shock and death.

However, she said it needed to be shorn as soon as possible as Merinos were bred for the specific purpose of growing wool, and leaving it as it was would be cruel. The sheep has been sedated to give it the best possible chance of survival.

"There could be infections, flystrike, [the coat] could prevent him from going to the bathroom. There could be a really nasty thing under that coat but we won't know that until we get there," she said.

While there have been calls to name the Canberra sheep, Ms Ven Dange cautioned the public on Wednesday against becoming attached.

"Just be aware that this fellow might not survive, we just don't know yet, so if we name it now there might be some heartbreak."

Early guesses have put the fleece at several years' growth.

Canberra Times