Check Out Kylie Jenner's See-Through Birthday Suit

Kylie Jenner got her birthday party started early -- and she did it partially nude ... naturally.

The soon-to-be 19-year-old rolled deep Sunday night with her whole 'KUWTK' krew into The Nice Guy for a huge party ... 10 days before her actual born day.

Kim Kardashian showed up with a new short 'do ... and Tyga also showed up, but the birthday girl could not be upstaged.

KJ was the sheer winner.