Rigel XVI (also called Yagthar) was a planet located in the galaxy's Beta Quadrant, the sixteenth planet in the Rigel star system in Federation space.

It was a medium-sized class G planet, covered with a sludge of helium and methane ice. Knots of chaotic space were found all over its surface and along its orbital path, a by-product of ancient and dangerous experiments performed on the planet by the First Orion Empire. (Decipher RPG module: Worlds)