Hearst has raided Conde Nast to hire Glamour’s No. 2 editor, Jill Herzig, to be the new editor-in-chief of Redbook.

Herzig replaces Stacy Morrison, who resigned two weeks ago. Her last day was Friday.

Herzig starts on May 3.

The Post’s Media Ink last week flagged Herzig as the frontrunner for the job, and predicted that Hearst Magazines boss Cathie Black was going to make her decision within the week.

Now the hard work begins: Herzig will have to try to reverse a slide in newsstand circulation as the 100-year-old magazine tries to find its footing in a competitive market.

Insiders said the magazine lost at least several million last year and had seen ad pages dip again in the first quarter, even as other magazines in the Hearst stable begin recovering from the ad slump.