12:15 PM PT -- According to the divorce docs, obtained by TMZ, Wendy says "irreconcilable differences" led to the end of the couple's marriage. The docs state a "breakdown" of the marriage over a period of at least 6 months. She wants the court to determine an "appropriate amount" of child support ... even though their son, Kevin Jr., is over 18.

11:46 AM PT -- A personal rep for Wendy tells TMZ, "Kevin is supportive of Wendy and they are working through this process together."

Wendy Williams is finally calling it quits on her marriage, amid tons of cheating rumors -- she just filed for divorce from her husband Kevin Hunter ... TMZ has confirmed.

Sources on Wendy's talk show tell us ... Kevin was served with the divorce papers Thursday morning at the studio. We're told extra security was on hand in case Kevin got enraged about the split, but he didn't.

The split comes after nearly 22 years of marriage, and most recently ... Kevin's alleged mistress, Sharina Hudson, having a baby.

Wendy is already ditching her wedding ring ... she wasn't wearing the massive rock during Thursday's episode of her show, although she made no mention of filing for divorce.

It's quite a change of tune for Wendy. Remember, it was just a few weeks ago when we got her out in NYC and she was flashing her ring and brushing off questions about Kevin's alleged affair.

Wendy's been going through a rough patch lately -- living in a sober house and getting round-the-clock help to deal with addiction issues.

As we first told you ... Wendy and Kevin were still working together on set, and while it was super awkward for some people on the show, the couple were amicable with one another and showing no overt signs of hostility. But clearly, she reached a breaking point.

Wendy and Kevin first met at an ice skating rink in 1994, getting hitched 3 years later. They have one child together, son Kevin Hunter Jr.