The effects of Human Milk Oligosaccharides (HMOs) on the infant gut are profound, influencing gut microbiome development and health trajectories through toddlerhood. Various HMOs, their doses, and periods of supplementation have been investigated, with clinical evidence supporting the supplementation of five key HMOs. HMOs are now incorporated into infant formula to mimic the benefits of breast milk, while non-human oligosaccharides are also explored for their potential benefits. Safety profiles and regulatory considerations are critical in the use of HMOs, which has advanced through improved synthesis and production techniques for clinical application. Real-world examples and case studies demonstrate the benefits of HMOs, and ongoing research is uncovering new possibilities for their application in promoting infant gut health.