Gideon J. Mellenbergh is emeritus professor of Psychological Methods at the University of Amsterdam, former director of the Interuniversity Graduate School of Psychometrics and Sociometrics (IOPS), and emeritus member of the Royal Netherlands Academy of Arts and Sciences (KNAW). His research interests are in the construction of psychological and educational tests, psychometric decision making, measurement invariance, and the analysis of psychometrical concepts. His teaching was on a large number of methodological topics (design, measurement, and data analysis) for audiences that vary from freshmen to dissertation students. He (co-) supervised 89 PhD students who successfully defended their thesis. Recently, he taught courses on methodological consultancy for research master and dissertation students. He published in international methodological journals (e.g., Applied Psychological Measurement, Journal of Educational Measurement, Multivariate Behavioral Research, Psychological Bulletin, Psychological Methods, and Psychometrika), contributed to methodological books, and published the introductory textbook A Conceptual Introduction to Psychometrics.