Aldebaron III was the inhabited third planet of its star system. This Federation planet was the home to the Aldebaron colony and a Starfleet installation.
In 2265, the USS Enterprise made a stopover at this planet to pick up Doctor Elizabeth Dehner from the Aldebaron colony. (TOS: "Where No Man Has Gone Before")
In 2371, the Ferengi Belongo, nephew of Grand Nagus Zek, was detained on Aldebaron III by the local Starfleet authorities. (DS9: "Past Tense, Part I")
According to Startrek.com  and the Star Trek Encyclopedia (2nd edition, p. 6), this planet was the same as Aldebaran III.
"al-DEB-uh-ron" was the pronunciation for this planet's name from the script
pronunciation guide for "Past Tense, Part I".
The closed caption from the episode on DVD gave the name as Aldebaran III.