After nine months of negotiations across Hollywood, Marvel Entertainment has unexpectedly opted to sell the movie rights to its hit comic book franchise “X-Men” to 20th Century Fox, studio sources said Monday.

Rival Hollywood production executives said Fox came up with a package late Friday night that took the comic characters off the market.

Columbia Pictures, reportedly one of the most aggressive suitors for the property, was expected to snap up the film rights. However, Colpix failed to finalize a deal, leaving the “X-Men” open to Fox’s last-minute acquisition.

“X-Men,” about genetic mutants who use special powers to take down bad guys, is a hot comic book properties among pre-pubescents. It has long been Marvel’s top-selling comic book title, as well as one of the top-selling trading card issues in the non-sports market.

There is a Saturday morning animated program based on the characters on the Fox Children’s Network.

Marvel spokeswoman Pam Ruff did not return calls seeking comment on the transaction Monday.

However, the deal underscores the New York-based publishing company’s aggressive effort to spawn its own franchise to compete with Warner Bros.’ “Batman” and “Batman Returns.”

Fox sources said the live-action film adaptation of “X-Men” will be put on the development fast track. Destined to be a big budget property, “X-Men” gives Fox a recognized franchise to draw on for summer and Christmas tentpoles.

The project does not yet have a producer or writer attached.