Nancy Cartwright -- the voice of Bart Simpson -- is a defendant in a lawsuit involving her fiance's suicide, a failed construction project, and the Church of Scientology ... this according to documents obtained by TMZ.
In the suit, the American Safety Casualty Insurance Company claims a construction company run by Stephen Brackett -- Nancy's fiance at the time -- was hired to fix up a restaurant in 2008. ASCIC issued an insurance policy to Brackett to cover the work ... and Nancy agreed to cover ASCIC's costs if anything went wrong.
ASCIC claims Brackett only did a portion of the work and "diverted contract funds" to the Church of Scientology, in which both he and Nancy were members. ASCIC says that when the project was halfway done, Brackett committed suicide and his company folded.
ASCIC claims it had to fork over roughly $260,000 to complete the project ... and that Nancy is refusing to cover the expenses, as promised.
ASCIC is suing her for the 260k plus a whole lot more.