Hashtags (i.e., the # symbol) are gaining increased popularity among social media users. However, despite their intense use, little is known about their meanings. Only a few published studies have investigated fragmented aspects of hashtags and treated them as a functional means to structure content. In this study, we provide evidence that hashtags’ meanings go beyond structuring or spreading content and represent an integral element of contemporary communication via social media. In particular, this study presents a series of six empirical studies, following traditions in grounded theory and measurement theory research, to systematically assess motivations for using hashtags. The results uncover the existence of 10 different motivations for use (amusing, organizing, designing, conforming, trendgaging, bonding, inspiring, reaching, summarizing, and endorsing). In addition, we show how these motivations differ between platforms and also relate to different patterns of social media behavior. The results contribute to a better academic understanding of social media, provide managers with profound insights and can guide marketing tactics with hashtags.