We report the observation of a quantum anomalous Hall effect in twisted bilayer graphene showing Hall resistance quantized to within .1% of the von Klitzing constant h/e 2 at zero magnetic field. The effect is driven by intrinsic strong correlations, which polarize the electron system into a single spin and valley resolved moiré miniband with Chern number C = 1. In contrast to extrinsic, magnetically doped systems, the measured transport energy gap ∆/kB ≈ 27 K is larger than the Curie temperature for magnetic ordering TC ≈ 9 K, and Hall quantization persists to temperatures of several Kelvin. Remarkably, we find that electrical currents as small as 1 nA can be used to controllably switch the magnetic order between states of opposite polarization, forming an electrically rewritable magnetic memory.