Phosphorus (P) is a key macromineral essential for numerous physiological processes, including energy metabolism, skeletal mineralization, and cellular signaling. In dairy cattle, its homeostasis is tightly regulated by parathyroid hormone, calcitriol, and fibroblast growth factor 23 (FGF23). Phosphorus deficiency is common during the transition period and is associated with reduced milk yield, anemia, muscle weakness, and immunosuppression in severe or prolonged cases. This review summarizes the current understanding of phosphorus metabolism in ruminants, emphasizing differences from monogastric species, hormonal regulation, and the clinical manifestations of deficiency. Particular attention is given to postpartum hypophosphatemia, its relationship with acute-phase proteins, and the pathogenesis of postpartum hemoglobinuria and recumbency. The review also discusses diagnostic methods for assessing phosphorus status, recent findings on FGF23 physiology in cattle, and including demonstrated effects of phosphorus imbalance on periparturient immune suppression and increased environmental phosphorus losses through manure. Maintaining optimal phosphorus nutrition is crucial for bovine health, productivity, and reduction in environmental phosphorus losses.