Pachekki*, Memer, Sparrials*. These are as described in GURPS Aliens.These are the only sentient aliens known to human civilisation as a whole. Most suitable worlds (about 75% of those with available liquid water for at least a few million years) have been found to contain indigenous life, but on only a fraction has it evolved to multicellular level, and on only a handful has sentience arisen. It is possible that other sentient species are known to the Pachekki, Memer, Chatka, and Ulhuqqa, since their spheres of knowledge extend well beyond human-space.
Larrokites*, Chatka*, Varg*, Ulhuqqa. These are described in a separate document.
The homeworlds of the Pachekki (Jidikki), Sparrials (Lirria), Larrokites (Larrok), Chatka (Ichik), and Varg (Zurgen) are within human- space. The Ulhuqqa homeworld is somewhere beyond the human-Ulhuqqa border. No humans have any idea where the Memer homeworld is.
Several worlds hold evidence of Precursor civilisations - long extinct species who built artifacts and left extant remains. There is no evidence to suggest that any of these Precursors possessed technologies or powers beyond the currently understood limits of science and technology. Precursor remains are studied vigorously as a branch of archaeology.