This book provides an overview of marginal zone lymphoma (MZL) for healthcare professionals and others with an interest in this blood cancer. It summarizes what is known about the pathophysiology of the disease, and discusses the importance of accurate diagnosis, staging, and prognosis, together with existing approaches to treatment and monitoring, including the latest evidence for new therapies in the relapsed/refractory (R/R) setting. With an eye to the future, it also reviews some of the therapies in development, which may ultimately improve quality of life and ensure better outcomes for patients with MZL.