Knowledge of the lymphatic drainage of the human organs is of great importance in oncology. The lymphatic system consists of vessels connected with masses of lymphatic tissue known as lymph nodes. The first or regional lymph nodes drain to other, secondary and tertiary, lymph nodes and finally to lymphatic trunks, the thoracic duct and the right lymphatic duct. The thoracic duct enters the venous system at the junction of the left internal jugular and subclavian veins, and the right lymphatic duct at the junction of the right internal jugular and subclavian veins. The right lymphatic duct drains the right side of the head, neck and thorax, the thoracic duct the rest of the body. A dilated sac, the cisterna chyli is found at the beginning of the thoracic duct, present in about 50% of cases. The intestinal and lumbar lymph nodes drain to the cisterna chyli. The thoracic duct and cisterna chyli were discovered in the seventeenth century by Aselli, Pecquet and van Horne, whereas anatomical studies on the lymph nodes and lymphatic drainage of organ systems date largely from the nineteenth century and early twentieth century, especially the French School of anatomists (Sappey, Quénu, Poirier and Cuéno, Rouvière). The Italian Paolo Mascagni is known for the first complete description of the lymphatic system. Several lymph nodes received eponyms from various European countries. More recent clinical studies pointed at the sentinel lymph nodes, the first lymph nodes affected by metastases of a malignancy. Here, we summarize the lymphatic drainage from the head and neck, the breast, the lungs, the abdominal and pelvic organs, and the external genital organs, where most of the anatomical eponyms became popular. For further data on the authors quoted, reference is made to Part II (The Anatomical Eponyms from A to Z) and figures in this part.