Now that Kylie Jenner just turned 18, Tyga will no longer be the butt of all statutory rape jokes. (Instead, he can be the tranny joke punchline...)

That must have relieved T-Raww, because he bought his no-longer-underage GF a $260,000 458 Ferrari convertible for her birthday.

The car showed up with a big bow attached.

Given that Tyga is being sued by multiple landlords for not paying his rent -- and his last album just flopped hilariously -- one has to wonder where he got the cash for the exotic sports car.

We're thinking Kylie -- who has been racking up the dough lately -- probably paid for the gift herself.