Fox reality chief Mike Darnell is leaving the network.

Darnell, best-known for greenlighting “American Idol,” will leave at the end of next month after 18 years at the network.

“I’m extremely grateful that Fox has offered me a new long term contract . . . but I’ve decided it’s time for a change,” Darnell said in a statement.

“With my current deal ending in June . . . I had to make a decision: either stay (and basically admit to myself I was going to retire at Fox . . . not a terrible choice) or leave and try something new.”

In addition to “Idol,” Darnell oversaw shows including “Family Guy,” “Joe Millionaire” and “Man vs. Beast.”