A Federation starbase to which Captain Lorca is ordered to withdraw the Discovery in 2256, an instruction he sidesteps in Into the Forest I Go.
Starbase 46 is a Starfleet installation some three hours from the planet Pahvo at warp five. It is mentioned in dialogue and marked on star charts, but has not been seen.
In the Discovery episode Into the Forest I Go, set in 2256, Admiral Terral orders Gabriel Lorca to abandon Pahvo and bring the USS Discovery back to the base, where he is to be decorated. Lorca complies in form only, travelling at warp instead of using the spore drive so that his crew has time to find a way to defeat the cloak of the Klingon Ship of the Dead.
After the victory, Lorca promises one last jump to the starbase, and that jump throws the ship into the mirror universe. In Despite Yourself the crew finds itself at the right coordinates but with no base in sight.