© The Author(s) 2020. There is now compelling evidence that people’s typical patterns of thinking, feeling, striving, and behaving are both consistent and malleable. Therefore, researchers have begun to examine the distinct sources of personality stability and change. In this article, we discuss traditional classifications of sources, review key findings, and highlight limitations and open questions in research on personality stability and change. We conclude by describing an integrative model and by outlining important directions for future research.