The Topin system was a star system proximate to both the Cardassian Union and the United Federation of Planets. At the center of the system is an unstable protostar, which generates large amounts of interference, making sensors and communications unreliable. (TNG episode: "Preemptive Strike")

In 2355, Starfleet Intelligence placed agents and equipment aboard the civilian freighter Ulrika's Hope in order to scan the Topin system during a scheduled run between Madellin Prime and Juhraya. (SCE eBook: Home Fires)

In 2370, Lieutenant Ro Laren lured the USS Enterprise-D to the Topin system using a false distress call, in order to steal medical supplies for the Maquis. (TNG episode: "Preemptive Strike")