We report a trinuclear dysprosium single-molecule magnet, [Dy3(μ3-CO3)(Clbbpen)3](CF3SO3)·6MeCN, which has a perfectly equilateral triangular structure. The Ising-like anisotropy of each Dy(III) site is oriented almost normal to the triangular plane, and magnetic dipole interactions between the spins cause an antiparallel Ising ground state. Crossing of the antiferromagnetic states by the ferromagnetic state occurs at ca. 0.2 T and gives rise to a characteristic step in magnetic hysteresis loops. This molecule thus serves as a perfectly triangular model system to explore frustrated Ising anisotropy.