Diffuse large B-cell lymphoma (DLBCL) is an aggressive and rare cancer of a type of immune cells (a white blood cell responsible for fighting infections) and the most common type of non-Hodgkin lymphoma. Follicular Lymphoma (FL) is a slow-growing type of non-Hodgkin lymphoma. The purpose of this study is to assess the real-world effectiveness of subcutaneous epcoritamab in adult participants with advanced DLBCL and FL. Epcoritamab is an investigational drug being developed for treating participants with DLBCL and FL. Approximately 700 participants will be enrolled in approximately 80 sites across 12-20 countries globally. Participants will receive epcoritamab as prescribed by their physician in accordance with local country label. Participants will be followed for up to 3 years. There is expected to be no additional burden for participants in this trial. Participants will attend regular visits during the study at a hospital or clinic according to their routine clinical practice.