Abstract: Freshwater cyanobacterial blooms occur globally, with phosphorus (P) being a key limiting nutrient for cyanobacterial growth and proliferation. Eutrophication is widely recognized as the primary driver of cyanobacterial dominance. However, even under extremely low phosphorus conditions, cyanobacteria can maintain high biomass levels. A potential intrinsic mechanism involves their ability to substitute phospholipids with non-phosphorus lipids (e.g., sulfolipids and glycolipids), thereby reducing cellular phosphorus demand and overcoming P limitation, which grants them a competitive advantage to form blooms. This review synthesizes strategies employed by typical bloom-forming cyanobacteria to regulate lipid metabolism under phosphorus stress, particularly through replacing phospholipids (e.g., phosphatidylglycerol, PG) with sulfolipids (e.g., sulfoquinovosyldiacylglycerol, SQDG) and glycolipids (e.g., monogalactosyldiacylglycerol, MGDG; digalactosyldiacylglycerol, DGDG). The ecological implications of this adaptation mechanism are critically examined. By unveiling novel phosphorus-sparing strategies in cyanobacteria, this study provides new insights into the mechanisms driving bloom formation and proposes innovative approaches for bloom control. This is particularly significant given that current prevention and control methods primarily focus on reducing nutrient loads, underscoring the need to revisit conventional eutrophication management paradigms.