This study utilized a systematic-narrative hybrid strategy to overview the concept of skill gap and its measuring approaches. Using the PRISMA guidelines, we conducted a systematic search in January 2023 to retrieve English records from the ProQuest, ScienceDirect, Scopus, and Web of Science databases using the keywords “skill gap,” “skill mismatch,” “skill shortage,” “identifying or measuring,” and “Industry 4.0.” In total, 40 articles met our predefined inclusion criteria, and we analyzed them descriptively and qualitatively using thematic analysis and constant comparisons. We found that skill gaps certainly exist, and that concerns about growing skill gaps have been raised worldwide. Our literature review also revealed the need for a common understanding of skill gaps. Considering this, we provided a skill gap definition. Skill gaps are an extremely nuanced phenomenon, so paying careful attention to their definition and interrelating social, environmental, and technological factors when measuring them is essential. Since we found very few studies that employed different methods and perspectives to research the concept, more research is needed to map actual skill gaps, which can only be done by considering different perspectives and measuring approaches.