Indolent lymphoma, also known as low-grade lymphoma, is a group of slow-growing non-Hodgkin lymphomas (NHLs). Because they spread slowly, they tend to have fewer signs and symptoms when first diagnosed and may not require immediate treatment. Symptoms can include swollen but painless lymph nodes, unexplained fever, and unintended weight loss.

There are several subtypes, the most common of which is follicular lymphoma. Others include cutaneous T-cell lymphoma, marginal zone lymphoma, chronic lymphocytic leukemia, and Waldenström macroglobulinemia.

Indolent lymphoma accounts for 41 percent of all non-Hodgkin lymphoma cases in North America and Northern Europe. It mainly affects older adults, and affects men and women almost equally. White people have higher incidence rates than black and Asian people, but the cause of these disparities is poorly understood.

Indolent lymphoma is usually considered incurable without the use of allogeneic stem cell transplantation, unless the disease is localised. However, due to its slow-growing nature and response to treatment, patients often have prolonged survival.

Patients normally present with painless, swollen lymph nodes, often in the neck, armpit, or groin. Some have swollen lymph nodes inside their body, such as in the chest or abdomen, which can go undetected until they become very large and cause symptoms like cough or abdominal pain.

The cause of indolent lymphoma is unknown, but research has identified a number of factors that increase risk.^{[citation needed]}

The risk of developing indolent lymphoma increases with age. Although the disease can occur at any age, it mainly affects older adults. It is uncommon in people under age 40 and very rare in children.^{[citation needed]}

People with HIV are at slightly higher risk than the general population. For patients who were previously diagnosed with an AIDS-defining illness, the risk of developing indolent lymphoma is 14-fold higher.