They'll be available in silver, in what the organisation says is keeping with the tradition of crossing a new-born baby's palm with silver to offer prosperity.
The coins can also be bought in gold to symbolise a royal celebration.
Princess Charlotte, the second child of the Duke and Duchess of Cambridge, will be christened by the Archbishop of Canterbury in July.
A private service will take place at St Mary Magdalene Church on the Queen's Sandringham estate on July 5th.
Most Revd Justin Welby also baptised the royal couple's son George.
Shane Bissett, director of commemorative coins at the Royal Mint, said: "As a British institution, the Royal Mint has played a central role creating works of art as official commemorations of landmarks in the history of the Royal Family for hundreds of years.
"These coins will be a fitting addition to that long tradition. It is only appropriate that we commemorate this significant occasion with the release of a special coin, just as we celebrated the christening of Prince George."
