Shannen Doherty Files for Divorce from Kurt Iswarienko in Nasty Split

Shannen Doherty is pulling the plug on her 11-year marriage, filing for divorce from Kurt Iswarienko ... and we're told things are nasty behind the scenes.

Shannen filed docs, obtained by TMZ, Friday in L.A. stating the two have been split up since back in January ... they were married in October 2011 and did not have any kids together.

Shannen's rep, Leslie Sloane, tells TMZ ... "Divorce is the last thing Shannen wanted. Unfortunately, she felt she was left with no other option. You can contact Kurt's agent, Collier Grimm at PICTUREKID as she is intimately involved." Not hard to read between the lines.

Sources close to the estranged couple tell us Shannen's living with stage 4 cancer and the divorce is very acrimonious ... which makes things all the more difficult.

According to the docs, filed by Disso Queen Laura Wasser, Shannen is asking for spousal support, but for it not to be awarded to Kurt. We're told there was no prenup.