Molecules can exist in a wide range of astrophysical environments, from the extremely cold regions between stars to the atmospheres of stars themselves.

To date, around 140 molecular species have been tentatively or definitively identified in interstellar or circumstellar clouds, while about 50 have been identified in studies of comets in our solar system. Numerous isotopomers have also been observed.

Some detections reported on these pages may be controversial, but all are taken from the peer-reviewed astronomical literature. A questionable identification may be removed at a later date if circumstances warrant.

J. Crovisier has amassed a comprehensive compilation of species observed to date in the interstellar medium, in comets, or in non-terrestrial planetary atmospheres, plus additional ones which may prove to be found.