According to Official Guinness Records,
The largest gold coin weighs 1,012 kg (2,231 lb 1.24 oz), measures 80 cm (2 ft 7.49 in) in diameter, 13 cm (5.12 in) in thickness and is made from bullion with a purity of 99.99 per cent. The legal-tender coin was introduced on 9 February 2012 by the Perth Mint (Australia), with a face value of AUS$1 million (US$992,849.80;£623,930.51).
The coin, called the "1 Tonne Australian Kangaroo" features a Kangaroo and was created to promote Australia's official Kangaroo Gold Bullion Coin series.
For a complete list of 2012 records, please visit 2012 Guinness Records in Australia.