Lactoferrin (Lf) is a multifunctional iron-binding glycoprotein of the transferrin family that plays a central role in host defense, particularly in protection against infection and tissue injury. Abundantly present in colostrum, secretory fluids, and neutrophil granules, Lf exerts broad-spectrum antimicrobial activity against bacteria, viruses, fungi, and parasites. These effects are mediated by iron sequestration, disruption of microbial membranes, inhibition of microbial adhesion, and interference with host-pathogen interactions. Beyond its antimicrobial functions, Lf regulates pro- and anti-inflammatory mediators and mitigates excessive inflammation. Additionally, Lf alleviates oxidative stress by scavenging reactive oxygen species and enhancing antioxidant enzyme activity. This review summarizes the current understanding of Lf's biological functions, with a particular focus on its roles in microbial infections, immune modulation, oxidative stress regulation, and inflammation. These insights underscore the therapeutic promise of Lf as a natural, multifunctional agent for managing infectious and inflammatory diseases and lay the groundwork for its clinical application in immune-related disorders.