Last week Sinead O'Connor accused Arsenio Hall of being Prince's long-time drug dealer [click here if you missed that].
Arsenio just slapped Sinead with a defamation of character lawsuit...
According to reports Arsenio Hall filed a $5 million lawsuit against Sinead O'Connor describing the troubled pop star as "well known for her media antics and for seeking attention through inflammatory Facebook posts."
Arsenio, repped by legal pit bull Marty Singer, denies all charges.
