Algeron IV was the fourth planet of its star system.

In 2364, after a brief layover at Relva VII, the USS Enterprise-D set course for this planet. (TNG: "Coming of Age")

This planet was only mentioned in dialogue.
According to, Algeron IV might have been located close to the Romulan Star Empire and the namesake for the Treaty of Algeron.
According to Star Trek: Star Charts (pp. 61 & 66) and Stellar Cartography: The Starfleet Reference Library ("Stellar Cartography", p. 38; "Federation Historical Highlights, 2161-2385"), the Algeron system was located in the Beta Quadrant. The primary was an A-class star. In 2156, the Battle of Algeron, the first battle of the Earth-Romulan War, was fought in this system.