The biggest, heaviest and inherently most valuable gold coin in the world has been unveiled by the Perth Mint.

Weighing 1012 kilograms, it is more than a tonne of 99.99 per cent pure gold worth more than $53.5 million.

The giant coin is 80 centimetres wide, 12 centimetres deep, took 18 months to create and features a bounding red kangaroo on one side and the Queen on the other.

It is Australian legal tender and has a denomination of $1 million — well below its gold value.

Perth Mint chief executive Ed Harbuz said the coin was "the pinnacle of ingenuity and innovation".