Larrisint IV was a gas giant planet in the Alpha Quadrant and the fourth of seven in the Larrisint star system. The planet had a planetary ring system.
The Federation's secret Newton Outpost was located on a shepherd moon within Larrisint IV's rings. (DS9 novel: Sacraments of Fire)
The Changeling-like entity that escaped Newton Outpost in 2385 used the gravitational pull of Larrisint IV to "slingshot" itself out of the system towards the Bajoran system. (DS9 novel: Ascendance)