A new type of superstars developed with the rise of social media markets: social media superstars (SMS). The economic literature on the superstar phenomenon provides empirical evidence on different types of stars, above all athletes and musicians. This paper presents the first empirical work on SMS with original data from YouTube. Using various econometric techniques, we analyze a unique sample of 200 YouTube stars out of four different video categories to shed light on this new phenomenon. Beyond applying classic economic concepts on superstars by Rosen, MacDonald, and Adler, we contribute to extending the literature toward attention economics and the concepts of audience building (audience attraction and maintenance). In our empirical analysis, we find evidence supporting an inverse U-shape influence of upload frequency on the success of SMS. Moreover, we find empirical evidence that the duration and experience in the market have a significant influence on social media success. Eventually, we derive implications for superstar theory, SMS management, service providers, and advertisers.