Not one, not two, but three: Totalsyntheses of amphidinolides B, G, and H, which exhibit strong, nanogram‐scale cytotoxicity against various tumor cell lines, have been executed. The synthetic strategy relied on implementation of a diene construction protocol and a diastereoselective aldol process. The 26‐ and 27‐membered macrocyclic lactone rings were efficiently constructed by using ring‐closing