The company Mark Cuban handed $2 million dollars on "Shark Tank" to scare the living daylights out of people ... is now getting sued for an allegedly terrifying injury.

Ten Thirty One Productions famously creates frightening Halloween experiences, and one of them was on NYC's Randall's Island in 2016 -- the Haunted Hayride. A woman who was attending says a fog machine fell during her fright night ... and banged her on the head.

In the suit, obtained by TMZ, she says she suffered serious and permanent injuries that have prevented her from performing her regular duties.

She's suing Ten Thirty One -- which also produces the "Great Horror Camp Out" -- to compensate her for her medical costs, plus damages. She is not suing Cuban.