Rigel V

From Memory Alpha, the free Star Trek reference

Rigel V is the fifth planet in the Rigel system, and homeworld of the Rigelians. (TOS: "Journey to Babel")

Presumably, Rigel V is Class M, as is Vulcan.

Rigel system
Rigel
Rigel II • Rigel III • Rigel IV • Rigel V • Rigel VII • Rigel X • Rigel XII