KATER Gordon, who won an Emmy just a month ago as the co- writer of “Mad Men,” has been dumped.

No reason was given for her abrupt departure but it brings to an end one of the sweeter rags-to-riches stories that has been so much a part of the “Mad Man” phenomenon.

Gordon started off as the assistant to the show’s creator Matthew Weiner and worked her way up after three seasons to a job as a full-time writer — and the co-author of the all-important season finale.

The Web site Deadline Hollywood broke the news of Gordon’s unexplained departure — no one is yet calling it a firing — yesterday.

“We think [Kater’s] done a great job, particularly for someone whose career has progressed so quickly,” a source told the Website in an email.

“Now, however, Matt has reluctantly decided that their relationship has reached its full potential.”

Gordon is listed as the co-writer of the season 2 episode “Meditations In An Emergency,” which won the Emmy for best drama script last September.

The show has finished filming this season.