This book constitutes the 4th Challenge on Diabetic Foot Ulcers, DFUC2024, held in conjunction with the 27th International Conference on Medical Image Computing and Computer-Assisted Intervention, MICCAI 2024, in Marrakesh, Morocco, on October 6, 2024. The 8 full papers presented in this book together with 2 invited papers were carefully reviewed and selected from 11 submissions. The task of DFUC 2024 was on self-supervised learning in ulcer segmentation, for the purpose of supporting research towards more advanced methods to overcome data deficiency and unlabelled data.