Microsoft's best known flagship franchise has now surpassed the 50 million units sold mark.

Halo: Combat Evolved was launched for Xbox in 2001 and proved incredibly popular at the time, though it was Halo 2 that ignited the franchise player's passion for online gaming.

Halo 4 has reportedly now sold over 4 million copies since launch and will surely grow over the holiday period.

Microsoft released this press statement regarding the sales of Halo.

“The "Halo" franchise is an award-winning collection of properties that has grown into a global entertainment phenomenon. Beginning with the original "Halo: Combat Evolved" (2001), the critically acclaimed and record-shattering series of games has since inspired multiple New York Times bestselling novels, comic books, action figures, apparel and more.

Published by Microsoft Studios, the "Halo" franchise of games is exclusive to the Xbox 360 video game and entertainment system and the Xbox LIVE online entertainment network. To date, more than 50 million copies of "Halo" games have been sold worldwide, driving more than 5 billion hours of gameplay by people connected to Xbox LIVE.”

343 Industries, the team behind Halo 4 have already announced they are creating artwork, concepts and prototypes for the next Halo game.