Syntagus Theluv, also known as T-B 13, was a planet, the thirteenth planet of the Tri-Betaline star system. With a class M environment, this world was the homeworld of a humanoid species known as the Theluvians.

In 2364, the USS Enterprise-D entered orbit of the planet to conduct a general survey. As the sensor scans were being conducted, the Enterprise was contacted by the Theluvians, who expressed their desire to meet the Enterprise crew and establish a dialog with them. With this in mind, Commander William T. Riker led an away team down to the surface, but instead of finding themselves in the planet's capital city, they found themselves in a forest clearing, and under attack by a Tripolian hellblazer.

Eventually, the away team were able to overcome the hellblazer and learned that even though it appeared that adults were attacking them, it turned out that the Theluvians age in reverse, and the children are the adults on Syntagus Theluv. (TNG - Beginnings comic: "... Where No One Has Gone Before!")

Planets visited by the USS Enterprise-D
2364	Earth • Deneb IV • Archaria III • Ligon II • Styris IV • Omicron Theta • Gamma Tauri IV • Delphi Ardu IV • Peacekeepers' World • Parliament • Rubicun III • Quadra Sigma III • Haven • Torona IV • Angel I • Starbase 74 planet • Bynaus • Tigan VII • Syntagus Theluv • Tarod IX • Faltos • Persephone V • Mordan IV • Aldea • Velara III • Relva VII • Minos • Brentis VI • Treva • Vagra II • Ornara • Brekka • Vandor IV • Sarona VIII • Dytallix B
2365	'aucdet IX • Tenara • Epsilon Miranda V • DQN 1196 • Raimon • Feenix-Denn IV • Himalias V • Thiopa • Gravesworld • Ramatis III • Solais V • Gagarin IV • Elysia • Iconia • Pacifica • Bringloid V • Mariposa • Drema IV
2366	Kavis Alpha IV • Tau Cygna V • Galorndon Core • Acamar III • Orelious IX • Bre'el IV • Cassiopeia Delta VII • Archer IV • Betazed • Vulcan • Rutia IV • Jouret IV
2367	Saturn • Earth • Turkana IV • Camus II • Tagus III • Adelphous IV • Evadne IV • Qo'noS
2368	Qo'noS • El-Adrel IV • Valo I • Valo II • Qualor II • Vulcan • Galorndon Core • Hermeticus II • Votar VII • Sindar • Tessen III • Rajatha Prime • Earth
2369	Frigis • Hobson Delta II • Bajor • Eloh • Riat • Atrea IV • Nervala IV • Enoch VII • Earth
2370	Terrellian crashsite world • Marijne VII • K'Trall • Dessica II • Barradas III • Calder II • Vulcan • Kesprytt III • Enoch VII • Dyson Sphere • Hera • Atrea IV • Vacca VI • Dorvan V • Hera • Krantin • Syng II • Earth
2371	Sindikash • Thanet • Ntignano • Damiano • Veridian III