DO NOT, we repeat, do not steal anything off Urijah Faber's porch ... 'cause the UFC legend will literally come for you wieldin' a bat ... ready to crack skulls.

Let's explain ... just last week someone jacked a $500 stroller from right outside of Faber's NorCal home.

The stroller is for Urijah's 1-year-old baby girl, Cali ... so he was PISSED.

Faber hopped in his car and went out looking for the stolen goods ... and that's when he spotted a familiar-looking stroller at a homeless encampment only a few blocks from his house.

Now, the California Kid is still a badddd man when it comes to fighting ... but not even the UFC Hall of Famer was brash enough to walk into a potentially violent situation with only his fists.

So, Faber put on surgical gloves (COVID-19 protection), grabbed a wooden baseball bat, a bullwhip (yes, that's right) ... and marched his ass straight into the camp.