Canopus Planet was an inhabited planet in the Canopus system.
In 1996, the poet Tarbolde wrote the famous love sonnet "Nightingale Woman" on this planet. (TOS: "Where No Man Has Gone Before")
In the script of "Where No Man Has Gone Before", this planet was referred to as "a Canopus planet", suggesting a probability that – as originally intended – the name "Canopus" was in reference to the planet's inhabitants and that the planet itself was to remain unnamed.
Presumably, this planet was located in the Canopus system.
The bios in Star Trek: Starship Creator speculate that Lieutenant Nara (TNG: "Eye of the Beholder") was from Canopus Planet.