This book constitutes the proceedings of the First MICCAI Challenge on Ultra-Widefield Fundus Imaging for Diabetic Retinopathy, UWF4DR 2024, held in Marrakesh, Morocco, on October 10, 2024. The 17 full papers included in this book were carefully reviewed and selected from 17 submissions. They present methodologies and results of the challenge which consists of three clinically relevant subtasks: image quality assessment for ultra-widefield fundus (Task 1), identification of referable diabetic retinopathy (Task 2), and identification of diabetic macular edema (Task 3).