Quinoline, C₉H₇N, is a bicyclic, N-containing aromatic compound that has been sought in interstellar sources unsuccessfully on at least two occasions. In 2005, Charnley and coworkers searched for quinoline, isoquinoline, pyridine, and pyrimidine toward carbon-star sources CRL 618 and IRC +10216. A subsequent search reported in 2017 by Cordiner and co-workers was not able to detect quinoline, isoquinoline, or pyrimidine toward TMC-1. Three telescopes were used in the two studies: the 12m (36 foot) telescope at Kitt Peak National Observatory and the 30m IRAM telescope were used for the 2005 search, while the Green Bank Telescope was used for both studies.

Quinoline is a member of the polycyclic aromatic nitrogen heterocycle (PANH) family. It is thought to be a potential interstellar precursor to the subgroup of PANHs that are very important to life and its origin, the nucleobases.