EXCLUSIVE

11:38 AM PT -- Tyga's reps tell us, "These, like other allegations, are completely false. This was a business relationship that went sour and was ended last year. We learned of the complaint via TMZ and are aware that individuals will continue to attempt to cash in on Tyga's success."

Tyga screwed a woman -- not named Kylie -- by lying to her, and jacking her concept for a clothing company to the tune of more than a MILLION bucks ... or so she claims in a new lawsuit.

According to the docs ... Tyga and Chuon Guen Lee formed the clothing line Last Kings in January 2013 -- and she says Tyga promised to heavily promote the line and get it on shelves in the popular clothing chain, Tilly's.

Lee says none of those things happened, and then Tyga made off with more than half a mil in merch. The real kick in the gut -- she says he started another company with another partner, and cleverly named it ... Egypt Kings.

Needless to say, Lee is not amused by the wordplay. She's suing Tyga and his new partner for $1.6 mil, plus damages.