11/16 -- A rep for Missy's team tells us, "There is not now and never was any 'agreement' between Missy Elliott and Terry Williams. As the exclusive owner of her own lyrics and vocals that she created, Missy is not obligated to pay Terry Williams money."

He continues, "These claims against Missy are completely meritless and without any basis in fact or law, and are simply another facet of the original scheme that was devised to artificially extract money from Missy by exploiting the fact that Terry Williams, in his capacity as a music producer, happened to have recordings of Missy from more than 20 years ago."

Missy Elliott and Timbaland cranked out a big hit for Aaliyah without ever paying the guy who actually co-wrote and produced it ... at least that's what the songwriter claims in his new lawsuit.

According to legal docs, obtained by TMZ, Terry Williams helped Missy write and produce a song called, "Heartbroken" around 1994 or '95. The track was eventually released by Aaliyah in 1996, but Terry says she only got it because Missy sold the song without his permission.

Timbaland produced the Aaliyah track -- and in the lawsuit, Terry says neither he nor Missy ever compensated him.

Terry claims he had an agreement with Missy to share profits from the song. According to the suit, the version Timbaland and Aaliyah released was almost identical to his ... same sound and same lyrics.

Terry claims Missy kept his contribution hidden ... presumably from Timbaland and Aaliyah.

Aaliyah's version came out on her "One In A Million" album, which sold 8 million copies worldwide.