The couple, who were visiting Mrs Croker's daughter, were driving back from Burnie at about 7pm last Saturday.

"We were getting close to Rosebery," Mrs Croker said. "It was cold, there was misty rain and it was wet. There was no-one on the road. We were driving down the hill about a kilometre from the town.

"Suddenly a huge black cat leapt from the bank onto the road. It was enormous - the length was amazing. Between the tail and the head it was almost the full lane width, and about a metre tall.

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"It was fast; it ran in front of us. It turned and faced the car. It had orangey eyes, but it was pitch black with no markings.

"Like a typical cat, it came across in front of the car, spun its head around and we had the lights on high beam.

"It had a look at us, and disappeared very quickly."

Mrs Croker said she was frightened when she realised there was such a huge animal roaming near the town.

"You do question your own judgement. Graham pulled the car up and said, 'We have just experienced a black panther'.

"It left you speechless and wondering, and a surreal feeling."

Mrs Croker said once the shock had worn off, they felt tremendously privileged.

"Not many people would have seen this. This is a mystery cat. It's living in very, very thick bush in a very untouched, pristine area. It's hardly penetrable."

Mrs Croker said when she reported the animal to the police, they were unimpressed and asked why she was calling them.

West Coast Council Mayor Phil Vickers said he'd had no reports of an animal like that, but people in the area should keep their eyes peeled.

"I've had no reports, but that doesn't mean that the people didn't see what they saw."

Trowunna Wildlife Sanctuary operations manager Darren Rumble said the only thing he could think of was a large feral cat.

"You hear a lot of black cat panther stories, but not in Tasmania," Mr Rumble said.

Black panther sightings in NSW have been happening for decades.

In 2001, a freedom-of-information request revealed the state government had been keeping a secret file on panthers.

In 2002, a NSW government inquiry found it was more likely than not a colony of big cats was roaming Sydney's outskirts and beyond.

But a 2009 Department of Primary Industries report concluded that "there is still nothing to conclusively say that a large black cat exists".

It said big cat sightings had been happening in NSW for more than 100 years.

More than 500 accounts had been logged across NSW in more recent times in areas including the western fringes from the Hunter to Sydney.

American soldiers were said to have brought panthers and pumas to Australia as mascots in World War II. Also, American gold miners brought big cats to NSW in the 1850s. And big cats were reportedly available on the black market years ago for $5000.

Big cats have reportedly escaped from zoos and circuses.