Kylie Jenner is about to start World War III ... between "Cash Me Ousside" girl and Honey Boo Boo's big sister!
HBB and Pumpkin arrived in NYC Tuesday night and a photog asked what they thought about Danielle Bregoli talking major trash on the Kardashians. Pumpkin's a huge fan of the K Krew, and quickly fired back on their behalf ... until her sis shut her down.
It's pretty hysterical -- Honey Boo Boo quickly warned Pumpkin about Cash Me's quick hands.
Still, 17-year-old Pumpkin vs. 13-year-old Danielle? Place your bets.