10:07 AM PT -- Kathy didn't wait long to respond to the news breaking, writing on X, "Well...s***. This sucks."

Kathy Griffin doesn't seem too nostalgic about anniversaries ... because she's decided to end her marriage, just as she and Randy Bick would have celebrated their 4th.

Kathy filed divorce docs Thursday in L.A. County, citing irreconcilable differences. According to the docs, obtained by TMZ, she and Randy have a prenup ... which she wants the court to enforce. Translation: no need for the judge to grant spousal support.

Randy, who's a marketing exec, and Kathy didn't have any kids together ... so, no issues with child support either.

Whatever went wrong, the breaking point was recent -- in the divorce petition, she lists Dec. 22 as their date of separation.

The soon-to-be exes tied the knot in a surprise wedding on New Year's Day 2020, and Lily Tomlin officiated the ceremony. Although they wed in the middle of lockdown, you can't really call it a pandemic marriage.

Kathy and Randy had been together for a long time before that -- they started dating in 2011, broke up in 2018 and then got back together the next year. This will be her second divorce.

Coincidentally, Kathy's going back on the road in 2024 ... her new standup show is called "My Life on the PTSD-List."