New 20-cent coins celebrating one of Australia’s most loved kid’s books have been released by the Royal Australian Mint

The coloured coins mark the 20th anniversary of Mem Fox’s Where is the Green Sheep? picture book and have already skyrocketed in price online.

The Royal Australian Mint has unveiled a new 20-cent coin celebrating one of the country's most beloved children's books.

The coloured coins mark the 20th anniversary of Mem Fox's Where is the Green Sheep? picture book and are already skyrocketing in price online.

The 20-cent coins feature the “bed sheep” reading a book, along with a green thought bubble of a blue, orange and red sheep.

There are three versions of the collectable coin available.

There will be 25,000 coloured 20-cent coins available with a themed card or a copy of the book. A further 3,000 gold-plated coloured 20-cent coins will be released with a deluxe edition of the book.

Author Mem Fox said she was thrilled for her book to be featured on a coin, while illustrator Judy Horacek said she “would never have dreamed” that her sheep would appear on a coin.

“Where is the Green Sheep? The answer is... on a coin! What a thrill it is to have the green sheep hit such heights,” Fox said.

“I'm very grateful to everyone involved in creating the original book and madly grateful to the Mint for honouring the book so beautifully in its 20th anniversary year. Like a coin, I'm spinning!”

Mint product developer Matthew Frawley said the release was the fourth in a series celebrating popular Australian kid's books. Previously coins included Animalia, Diary of a Wombat and Edward the Emu.

“Where is the Green Sheep? is one of those classic Aussie children's books that are always on high rotation for any parent and youngster,” he said.

“Gorgeously teaching kids about opposites and even the concept of ‘where’, all wrapped up in Mem’s addictive prose and Judy’s riotous illustrations.”

Despite only just being released, the collectable coins are already being listed for premium prices online likely due to their limited nature.

The 20-cent coins are being listed for up to $55 each on eBay, which is nearly three times their RRP.

Meanwhile, the gold 20-cent coins with the book are for sale for up to $299.99, more than three and a half times their RRP.

It comes after the Mint released collectable $1 coins featuring Australia's favourite blue heeler, Bluey, earlier this year.

A new range of collectable Bluey coins and stamps will be coming to Australia Post on September, 2.

These coins were recently the subject of a police investigation after a warehouse worker allegedly stole $630,000 worth of the rare coins from the back of a truck in Sydney.

How can I get the 20-cent coin?

The 20-cent Where is the Green Sheep? coin is now available for purchase via the Mint Contact Centre, the Mint Coin Shop in Deakin, and from participating authorised distributors.

The 20-cent green sheep coin with a card is $17.50, the coin with a book is $50, and the gold-plated coin is $85.

The Mint is also running three EQL online ballots to purchase the coins. Successful entrants will be notified via email within 24 hours.