Jenner has applied for a trademark for "Kylie Hair" -- a line to include hair care products -- shampoos, conditioners, oils, gels, mousse and dye. Kylie's plans don't just stop at what to put in your hair, she's also trying to lock down products to style it too ... dryers, curling irons and brushes.

Kylie's older sister, Kendall, also recently filed docs to trademark bags, clothing and hair accessories under her own name.

Kylie Cosmetics is already a giant brand -- it's made her a billionaire -- and Kylie Skin is set to be a massive success as well.

TMZ broke the story, Kylie filed to trademark "Kylie Baby" earlier this week ... a line to include strollers, cribs, bouncers, bottles and a whole lot more.

The Kylie Empire continues to spread its wings.