Tatooine, if u dont believe me here is a quote from wookiepedia about the sarlacc
Wookiepedia wrote:The largest known specimen of the species resided in the Great Pit of Carkoon, beneath the sands of the Dune Sea on the remote planet of Tatooine.
oh and no i did not cheat and look that up, I answered that and then needed proof so that u would believe me.
Fun Facts about the Sarlacc:
The Sand People believe that the Sarlacc gave birth to itself inside of the planet Tatooine.
It is believed that sarlacc can torture their food by using their worst fears against them.
Even after Boba Fett blew up the digestive system of the Tatooine Sarlacc and left it for dead, he later encountered a few of its underground tentacles that were still alive.
The Tatooine Sarlacc is thousands of miles long, some believe it stretches out all over the inside of the planet Tatooine
The most commonly believed way of how the Tatooine Sarlacc got there is that close to 70,000-100,000 years ago an old Tatooine Sarlacc gave birth to the newer Tatooine Sarlacc, and that before it reached larval stage a jawa found it, put it in water not knowing what it was, and brought it along. It grew and escaped the jar and got eaten by a spider creature, it then ate that spider creature from the inside out, and later when it reached its larval stage went out and started hunting other creatures, when it reached its adult stage it settled into the Great Pit of Carkoon.
There are also sarlacc on Aargonar, Dathomir, Oovo IV, and Socorro. If you believe that the Tatooine Sarlacc is not the largest Sarlacc, then it is one of the others.
It is also possibly on: Geonosis, Dosha, and Lok (these are uncomfirmed)