The significance of classic stars and so-called influencers, such as YouTube stars, as the new celebrities has significantly increased in marketing. Companies expect various advantages for their brands from these figures. The range of implementation options is enormous: from traditional product placement to influencer endorsements on social media. At the same time, marketing decision-makers are grappling with the growing complexity due to an ever-increasing number of potential partners. The nearly unlimited reach of platforms like YouTube, as well as formats like casting shows, allows virtually anyone to achieve fame almost overnight. Therefore, this collection addresses the major challenges of successful celebrity and influencer marketing and closes the current knowledge gap with the help of many experts from practice and academia.