The very woolly merino sheep was spotted wandering on its own near Mulligan Flats, a grassy woodland just outside the national capital Canberra, by bushwalkers who alerted local RSPCA officers.
The officers headed out to the area, but had to return this morning with reinforcements after noting the creature's size.
"It's definitely one of the biggest sheep we've ever seen," said Tammy Ven Dange, head of the RSPCA in the Australian Capital Territory, adding that the as-yet-unnamed animal was "four to five times its normal size".
"He's pretty stressed out at the moment. We're trying to keep him calm and hopefully tomorrow (Thursday) we're going to sedate him and shear him," Ven Dange told AFP.
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"Hopefully he doesn't go into shock during that process."
Merino sheep are bred for their sought-after wool and can experience health issues, or even die, if not sheared regularly, Ven Dange said, explaining why she tweeted her call for help.
"They sent through a photo and I've never seen such wool on a sheep before," Elkins told AFP, noting that on average, a sheep would grow seven centimetres of wool each year.
The animal's voluminous fleece could rival New Zealand's most famous sheep, Shrek, which was found in 2004 following six years on the loose after going missing from its herd in 1998.