Nicollette Sheridan: Files for Divorce ... Who Knew She Was Married?!

Nicollette Sheridan pulled a fast one -- on us, anyway. Turns out she tied the knot, the marriage fizzled and Nicollette just filed for divorce.

The former "Desperate Housewives" star and Aaron Phypers are dunzo just 6 months into their marriage ... this according to legal docs obtained by TMZ.

According to the docs, they separated a month ago.

Rumors swirled they had been mulling over marriage ... but there was never a clue they tied the knot.

Nicollette is asking the judge to reject any claim Aaron might make for spousal support.