King Charles III's image has only previously appeared on a coin featuring Albus Dumbledore from the Harry Potter series.
The coin is the third in a series celebrating the 25th publishing anniversary of Harry Potter and the Philosopher's Stone.
The King is shown on the coin's "heads" side, and the Hogwarts wizard is shown on the reverse.
It is "one of a small number" of coin collections, according to the Royal Mint, that will have their royal portrait changed.
The late Queen Elizabeth II was featured on the first two coins in the series, which featured images of Hogwarts and Harry Potter.
Jim Kay, the illustrator of Harry Potter and the Philosopher's Stone's first fully illustrated edition, is represented on all three coins.
Some of the coins in the collection are colored, and others have a "latent feature" that rotates in the light to reveal a lightning bolt and the number "25" to mark the anniversary year, as a nod to the magic that gave the series life.
According to the Royal Mint, the coins are popular around the world. At least one coin from the range has already been purchased by Harry Potter fans in 86 different nations.
Although the designs are on a 50p, the collector's items start at £11.
Fans can pay £20 for a colour version, and up to £5,215 for a £200 denomination gold coin.
Director of collector services Rebecca Morgan stated, "We are thrilled to be continuing our magical Harry Potter coin collection with Professor Albus Dumbledore appearing on his very own 50p.
The Harry Potter coin collection from the Royal Mint has received positive reviews from collectors all over the world, not only because the books have become a worldwide phenomenon but also because it is one of the few collections whose portrait will change throughout the series.
This collection of coins serves as a lasting remembrance of the fascinating transition from Britain's longest-reigning monarch to His Majesty the King's debut on UK coinage. ".
In 1997, JK Rowling's Harry Potter and the Philosopher's Stone first appeared on store shelves. The seven-part series of books about the mysterious wizarding world has seen worldwide sales of more than £500 million.
