Archaeal membranes are composed of ether-linked isoprenoid phospholipids ether-bonded to glycerol-1-phosphate and hence are distinct from the ester-linked phospholipids of bacteria and eukaryotes. This fundamental chemical distinction of phospholipids in these domains of life is also known as the lipid divide and reflects an early evolutionary divergence in membrane composition. Although the core structure of archaeal lipid is conserved, recent advances in environmental genomics and lipidomics have substantially expanded the known structural diversity of archaeal phospholipids. Here, we provide an updated overview of the structural diversity of archaeal phospholipids and summarize the key biosynthetic pathways involved in their formation. In addition, current evolutionary hypotheses associated with the lipid divide are discussed in the context of recent discoveries, offering new perspectives on the evolution and functional diversification of cellular membranes.