Manifold regularization is a technique that penalizes the complexity of learned functions over the intrinsic geometry of input data. We develop a connection to learning functions which are "locally stable", and propose new regularization terms for training deep neural networks that are stable against a class of local perturbations. These regularizers enable us to train a network to state-of-the-art robust accuracy of 70% on CIFAR-10 against a PGD adversary using $\ell_\infty$ perturbations of size $\epsilon = 8/255$. Furthermore, our techniques do not rely on the construction of any adversarial examples, thus running orders of magnitude faster than standard algorithms for adversarial training.