Zadar IV was a planet located somewhere in the galaxy's Alpha or Beta Quadrants, in orbit of the Zadar star system in Federation space. Zadar IV is known for expansive ocean ecosystems filled with fish and other lifeforms. The Zadarian dolphin lived in the oceans of this planet.
In the 24th century, Zadar IV was home to a Starfleet science outpost. Oceanographer Harry Bernard, Sr. was stationed on Zadar IV with his son Harry Jr. in the early 2360s. They lived on the beach and Harry Jr. often saw dolphins playing in the ocean there. These observations would later be the inspiration for his first attempt at sculpting. (TNG episode: "When the Bough Breaks"; ST references: Encyclopedia, Star Charts)
- Zadar IV could be presumed to be class M, or otherwise a pelagic planet, since there is oceanic life and humanoids living there, but which it might be was not established.