Human CCL19 (C-C motif chemokine ligand 19), also known as macrophage inflammatory protein-3β (MIP-3β) or EBI1 ligand chemokine (ELC), is a member of the CC chemokine family that plays a central role in lymphocyte trafficking and organization of secondary lymphoid tissues. CCL19 is produced primarily by stromal cells, dendritic cells, and macrophages within lymph nodes, spleen, and other secondary lymphoid organs. It signals through the CCR7 receptor to direct migration of naïve T cells, central memory T cells, regulatory T cells, and mature dendritic cells to lymphoid tissues, facilitating antigen presentation, T cell priming, and initiation of adaptive immune responses. In healthy individuals, CCL19 is essential for immune surveillance and maintenance of lymphoid architecture; however, expression may increase during infection, vaccination, chronic inflammation, and certain malignancies. Dysregulated CCL19–CCR7 signaling has been implicated in autoimmune diseases, chronic inflammatory disorders, and tumor metastasis, particularly in cancers that exploit CCR7-mediated pathways for lymph node dissemination. In clinical and translational research, human CCL19 is studied as a key regulator of adaptive immunity, lymphoid tissue organization, and immune cell trafficking, and as a potential therapeutic target in cancer immunotherapy and immune-mediated diseases.