The Thandon Cluster, alternatively called the Thandon Nebula, was a region found in the Corporate Sector of the Outer Rim Territories. This area displayed characteristics of both a star cluster and a nebula. The Authority Guardian Corridor, a well-known hyperlane, ran along its southern border. The Shaltin Tunnels hyperspace route cut through the western part of the Thandon Cluster. A third hyperlane also skirted the northern edges of the region, ultimately ending at the Dostra system within the Thandon Cluster.
Within the Dostra system was Brosi, the only inhabited planet in the Thandon Cluster, and home to the Brosins, a group of near-Humans. The Corporate Sector Authority eventually gained control of the Thandon Cluster, but struggled with the development of this isolated region. By 2 ABY, the Corporate Sector Authority had established mining operations on Brosi. At this point, the planet's population included Humans in addition to the Brosins, reaching a total of nineteen million inhabitants.
The initial mention of the Thandon Cluster occurred in Alliance Intelligence Reports, a 1995 sourcebook created for Star Wars: The Roleplaying Game by West End Games. Mike Vilardi provided the illustration of the Thandon Cluster planet Brosi in that book. Later, the 2009 reference book The Essential Atlas introduced the alternative name "Thandon Nebula" and located the region within grid square S-3.