Elon Musk and Grimes really followed through with their outta this world baby name … but they had to play a little ball to comply with California law.

According to the newborn’s birth certificate, obtained by TMZ, Elon and Grimes named their first child, X AE A-XII Musk. Seriously.

Mom and Dad had to get a little creative — as if the kid’s name wasn’t clever enough — to make their tyke all legal and stuff. As you know … Elon and Grimes’ baby boy was born last month, and they wanted to name him X Æ A-12 Musk.

As it turns out, the aeronautic name didn’t fly in Cali, where birth names must be limited to the English alphabet — no numbers or special signs.

The result, as you can see, is a first name X, middle name AE A-XII … and last name Musk. See? Roman numerals ARE good for something besides Super Bowls!

If ya missed it, here’s a breakdown on little X’s handle: X stands for an unknown variable, AE is like artificial intelligence or AI, and A-XII is the name of a 1960s USAF spy plane.

The pronunciation goes like this … X like the letter, AE is pronounced “Ash” and then your standard A-12. As in, X-ash-A12. Duh!

That’ll be fun on the playground.