Flo Rida -- I Am NOT That Baby's Daddy!

Mr. Rida is accused of fathering a son with a woman named Gloria Halloway. The kid was born earlier this year.

Flo's attorney, Sandy Becher, tells TMZ ... the rapper took a paternity test last month that ruled him out as the boy's father ... but he used a pseudonym to protect his identity.

But Halloway isn't buying it -- claiming she has yet to see a document with Flo's REAL NAME on it ... and her lawyer, Damon McDougal, tells us, "There is absolutely nothing to indicate that [Flo Rida] was sampled."

McDougal adds, "I really do feel that the only way we are going to get a reliable paternity test is going to be within the confines of some sort of court order."