BACKGROUND: Core stability has been reported to be important for improving performance in athletes. However, the variety of measures used to assess core stability has made it difficult to compare results across studies. In addition, there is a lack of consensus on precise definitions of core and core stability, which is a barrier to research in this field. OBJECTIVE: The overall purpose of this review was to summarize the definitions of core and core stability and measurements of core stability used in previous studies on athletes. METHODS: We searched four electronic databases (PubMed/Medline, SPORTDiscus, Web of Science and Science Direct) from their inception to October 2023. Studies evaluating core stability in athletes across all sports were included. We excluded case studies and case series, opinion pieces, letters to editors and studies not written in the English language. Two researchers independently assessed articles for inclusion and exclusion criteria and methodological quality. RESULTS: One hundred thirty-four studies were included, of which two were of high quality. The definitions of core and core stability varied widely, and ‘core’ was not defined in 108 studies and ‘core stability’ was not defined in 105 studies. The most used test protocol was the McGill test, which was used in 19 studies. CONCLUSIONS: There are multiple tests to measure core stability, and there is some confusion as to whether the measurement results represent core strength or core endurance. Future research papers should clarify the definitions of core and core stability, and consider core strength and core endurance separately.