This book constitutes the refereed proceedings of the 9th European Lean Educator Conference on Challenging the Future with Lean, ELEC 2023, held in 's-Hertogenbosch, the Netherlands during October 24-26, 2023. There are 24 full papers presented in this book were carefully reviewed and selected from 35 submissions. The conference and presenting papers aimed to encourage Lean practitioners, educators, and researchers to "Challenge the Future with Lean," examining how important societal issues such as war, healthcare, digitalization, and sustainability can be addressed through Lean thinking.