New disgusting allegations against Johnny Manziel -- who's being sued for more than $350,000 for allegedly treating a $50 MILLION mansion like a giant litter box ... according to a new lawsuit.
As we previously reported, Manziel's at war with the guy who owns the famous Weidlake Mansion in the Hollywood Hills ... where the QB allegedly stayed for most of the summer.
According to the lawsuit, Manziel and his pal entered an 8 month lease to stay at the pad but disappeared after 3 months ... after causing more than $187,000 in damages.