Sonic's Secret Underground Base is a location that appears in the Sonic the Comic series published by Fleetway Editions. It was the former headquarters of the Freedom Fighters, before its destruction at the hands of Dr. Robotnik. Originally this was the home to the kindly Doctor Ovi Kintobor, who had a vast underground laboratory stored down here along with his Retro-Orbital-Chaos-Compressor.
After the accident that caused him to become Doctor Ivo Robotnik, Sonic, Tails and the Freedom Fighters used the lab as their secret base and hid from Robotnik for many years. They installed Kintobor's personality from a Golden Ring and onto a computer system to allow them to keep track on Robotnik's forces. They also installed a Star Post in the base, to enable them to travel quickly between the Zones of Mobius.
After Sonic and Tails captured Robotnik on the Floating Island, they brought him to their base and held him captive. However, the duped Knuckles was able to track Robotnik and rescue him, this revealing the location of the base. After Robotnik's initial defeat on the Floating Island, he enacted his revenge by destroying the base and driving Sonic and his friends out into the open, where they continued to hide as "Bob Beaky's Travelling Circus".
- Sonic the Comic #21, "Girl Trouble, Part 1"
- Sonic the Comic #34, "Enter Knuckles, Part 2"
- Sonic the Comic #35, "Power of the Chaos Emeralds, Part 1"
- Sonic the Comic #36, "Power of the Chaos Emeralds, Part 2"
- Sonic the Comic #37, "Robotnik's Revenge, Part 1"
- Sonic the Comic #38, "Robotnik's Revenge, Part 2"