Concept inventories (CIs)--typically multiple-choice instruments that focus on a single or small subset of closely related topics--have been used in science education for more than a decade. This paper describes the development and validation of a new CI for astronomy, the Star Properties Concept Inventory (SPCI). Questions cover the areas of stellar properties (focussing primarily on mass, temperature, luminosity, and lifetime), nuclear fusion, and star formation. Distracters were developed from known alternative conceptions and reasoning difficulties commonly held by students. The SPCI was tested through an iterative process where different testing formats (open-ended, multiple-choice?+?explain, and multiple-choice) were compared to ensure that the distracters were in fact the most common among the testing population. Content validity was established through expert reviews by 26 astronomy instructors. The SPCI Version 3 was then tested in multiple introductory undergraduate astronomy courses for non-science majors. Post-test scores (out of 23 possible) were significantly greater (M?=?11.8, SD?=?3.87) than the pre-test scores (M?=?7.09, SD?=?2.73). The low post-test score--only 51.3%--could indicate a need for changing instructional strategies on the topics of stars and star formation.