Lymphadenopathy or adenopathy is a disease of the lymph nodes, in which they are abnormal in size or consistency. Lymphadenopathy of an inflammatory type (the most common type) is lymphadenitis, producing swollen or enlarged lymph nodes. In clinical practice, the distinction between lymphadenopathy and lymphadenitis is rarely made and the words are usually treated as synonymous. Inflammation of the lymphatic vessels is known as lymphangitis. Infectious lymphadenitis affecting lymph nodes in the neck is often called scrofula.

Lymphadenopathy is a common and nonspecific sign. Common causes include infections (from minor causes such as the common cold and post-vaccination swelling to serious ones such as HIV/AIDS), autoimmune diseases, and cancer. Lymphadenopathy is frequently idiopathic and self-limiting.