Ahmedeen was a planet with seas of liquid argon.

After biomimetic copies of Tom Paris and B'Elanna Torres were married aboard the duplicate USS Voyager in 2375, Neelix suggested a holoprogram of wind surfing on Ahmedeen for their honeymoon. (VOY: "Course: Oblivion")

This planet was only mentioned in dialogue.
The Star Trek Encyclopedia (4th ed., vol. 1, p. 13) locates this planet in the Delta Quadrant.