The Royal Mint, based in Llantrisant, said the silver coin was designed to be a collectable.
It has been created to celebrate "the Welsh spirit", it added.
The coin has been designed by sculptor Norman Sillman, who received his first commission from the Royal Mint back in 1958.
Director of commemorative coin, Anne Jessopp, said: "This Welsh Dragon £20 coin portrays the Welsh spirit and the excellence and craftsmanship of our workforce - something of which we are all so proud."
The organisation opened its new "Royal Mint Experience" to visitors in May.
A commemorative £20 coin featuring the Welsh dragon has been revealed by the Royal Mint in Rhondda Cynon Taff.