Carmen Electra was ambushed by her ex-husband Dennis Rodman at a Halloween party in Florida last night ... and extra security was called in to keep her safe ... TMZ Sports has learned.

Carmen was co-hosting a private "Fright Night" party in Boca Raton with Jonathan Cheban ... and was surprised when she saw Dennis waiting on the red carpet for her.

We spoke with multiple witnesses who tell us Dennis was NOT invited to the shindig (put on by The Law Offices of Berman and Berman) -- and Carmen was so shocked when she noticed him, that she waited in her limo for roughly 25 minutes while extra security was called in to watch her back.

Once she left the limo, we're told Dennis made a beeline for her ... and professed his love.
One source tells us Dennis even asked her to marry him again -- but she artfully dodged the question and laughed it off. We're told Dennis was kicked out of the party but kept sneaking back in.

We're told the interaction only lasted a few minutes -- but it was super awkward ... especially since Carmen just appeared on Oprah Winfrey's network and spilled her guts about their failed marriage.

In fact, she told O that her union with Rodman was super volatile -- "When it was good, it was amazing. And when it was bad, it was the worst."

Of course, Dennis and Carmen were married in 1998 ... but divorced a very short time later following a domestic violence incident in which they were both arrested.

We reached out to Dennis for comment -- so far, no word back.
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