Service innovation acts as society’s engine of renewal and provides the necessary catalyst for the service sector’s economic growth. Despite service innovation’s importance, the concept remains fuzzy and poorly defined. Building on an extensive and systematic review of 1,046 academic articles, this research investigates and explores how service innovation is defined and used in research. Results identify four unique service innovation categorizations emphasizing the following traits: (1) degree of change, (2) type of change, (3) newness, and (4) means of provision. The results show that most research focuses inward and views service innovation as something (only) new to the firm. Interestingly, service innovation categorizations appear to neglect both customer value and financial performance.