A cane toad so giant wildlife officers thought it was fake has been found in a north Australian rainforest.

The "monster" specimen is six times bigger than the average toad, weighs 2.7kg, and could break a world record.

Dubbed "Toadzilla", the animal was quickly placed in a container and removed from the wild.

Toads - which were first introduced to Australia in 1935 - are one of the country's most damaging pests and are now estimated to number in the hundreds of millions.

When park ranger Kylee Gray first spotted the massive amphibian while out on patrol in Queensland, she couldn't believe her eyes.

"I've never seen anything so big," she told the Australian Broadcasting Corporation.

"[It looked] almost like a football with legs. We dubbed it Toadzilla."

Her team quickly captured Toadzilla - believed to be a female - and returned to base to weigh her. They knew she would be heavy, but were surprised to find she could set a new world record.

The current Guinness World Record for the largest toad - 2.65kg - was set by a pet toad in Sweden named Prinsen in 1991.

Ms Gray says this giant specimen likely bulked out on a diet of insects, reptiles and small mammals.

"A cane toad that size will eat anything it can fit into its mouth," she said.

Toads have no natural predators in Australia and the poisonous species have wrought havoc on native animal populations.

Ms Gray isn't sure how old Toadzilla was - the species can live up to 15 years in the wild - but believes she has "been around a long time".

Toadzilla has since been euthanised, as is standard practice in Australia for the pests, and will be donated to the Queensland Museum.