Swine CCL3L1 (C-C motif chemokine ligand 3-like 1, also known as LD78β or MIP-1αP) is a chemokine closely related to CCL3 (MIP-1α) that plays a role in leukocyte recruitment and regulation of inflammatory immune responses in pigs (Sus scrofa domesticus). CCL3L1 primarily signals through the CCR5 receptor, and to a lesser extent CCR1, promoting chemotaxis of monocytes, macrophages, dendritic cells, natural killer (NK) cells, and activated T lymphocytes to sites of infection or tissue injury. In swine, CCL3L1 is produced by activated macrophages, dendritic cells, and lymphocytes in response to inflammatory stimuli such as pathogen-associated molecular patterns and cytokines including TNF-α and IL-1β. CCL3L1-mediated signaling contributes to host defense by coordinating immune cell trafficking and amplifying inflammatory responses during infections, including porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza virus, and bacterial respiratory pathogens involved in porcine respiratory disease complex. Because CCR5-mediated chemokine signaling influences antiviral immunity and immune cell activation, CCL3L1 may also participate in regulation of inflammatory lung responses during respiratory infections. As a regulator of leukocyte migration and inflammatory signaling, swine CCL3L1 is relevant in studies of host–pathogen interactions, immune regulation, and vaccine responses, and contributes to understanding chemokine networks that influence disease resistance and immune function in pigs.