Abstract Study question What does the collaborative document on adenomyosis terminology, classification, and diagnosis by ESGE, ESHRE, and WES provides? Summary answer This good practice recommendations paper offers guidance on the technical aspects, terminology, classification, and diagnosis of adenomyosis in women of reproductive age. What is known already The existing literature on adenomyosis terminology is heterogeneous and confusing. Various classification systems based on ultrasound and MRI have been proposed, yet none have gained international acceptance or clinical validation. The contradictory data on the diagnostic accuracy of these modalities further complicate adenomyosis diagnosis in reproductive-age women. Study design, size, duration A working group from ESGE, ESHRE, and WES has collaborated to write recommendations concerning the terminology, classification, and diagnosis of adenomyosis. Participants/materials, setting, methods Focusing on terminology, classification, and diagnosis, this good practice paper paves the way for further recommendations on the management and surgical treatment of adenomyosis in reproductive-age women. Main results and the role of chance The document overviews adenomyosis terminology and reviews proposed classification systems based on histology, ultrasound, and MRI, concluding with diagnostic recommendations. Limitations, reason for caution Owing the scarcity of evidence, these recommendations predominantly rely on clinical expertise. Wider implications of the findings The recommendations aim to enhance existing adenomyosis guidelines. Study funding/Competing interests All costs were covered by ESHRE funds, with no external funding for the development process or manuscript production.