Chris Brown Impostor SUES -- Rihanna Gave Me Herpes

Another bogus celebrity lawsuit has been filed in federal court ... this time, the troublemaker claims to be Chris Brown ... and he's filed an INSANE lawsuit against Rihanna.

TMZ has obtained the documents, filed in U.S. District Court in Tennessee ... in which "Chris Brown" is requesting a restraining order against Rihanna because he fears she will cause him bodily harm.

The suit contains the following (completely untrue) allegations:

-- "[Rihanna] gave me herpes and then when I threatened to file a lawsuit against her for not telling me she was infested with genital blisters she began to hit herself in the face and throw herself into walls just as Jim Carrey did in the movie 'Liar, Liar."

"Then she turned around and blamed me for the matter as a form of punishment."

-- "I woke up with three blisters on my penis ... this isn't just a regular case of American herpes, this is a case of Herpes from Barbados, which is most likely lethal."

The accuser is demanding $10 million ... along with "a restraining order against Rihanna and her case of genital herpes immediately."

TMZ broke the story ... someone claiming to be Selena Gomez's father filed another bogus lawsuit in Michigan -- accusing Justin Bieber of stealing his credit card for a penis enlargement.