Chris Brown isn't gonna take this lying down ... the singer claims he'll sue for defamation the model who claims Brown raped her in his Paris Hotel room earlier this week. The claim sent Chris into police custody for 24 hours and made headlines around the world for a guy famous for beating ex-girlfriend Rihanna back in 2009.

Brown was released without charges Tuesday after being questioned overnight by French police -- but Paris officials reserve the right to file charges at a later time, dependent on their investigation.

The 29-year-old's French lawyer, Raphael Chiche, said Brown vigorously denied the allegations and he is preparing to file the defamation lawsuit on behalf of his client: "A complaint for slanderous denunciation will be filed tomorrow with the public prosecutor of Paris."

A 24-year-old model -- not named for privacy reasons -- claims the singer and two other men raped her during a drug-fueled party in Brown's hotel suite at the Mandarin Oriental in Paris a week ago.