Beem et al. used a superconformal supercharge to localize N=4 Yang-Mills to a two-dimensional chiral theory.  I will discuss my work with Gaiotto, in which we analyze the holographic dual of this localization.  We argue that the same localization applied to type IIB string theory yields a topological string living on AdS_3 x S^3.  We build a holographic chiral algebra using Witten diagrams for this topological string theory, and show that the holographic chiral algebra is isomorphic to the large N chiral algebra in the planar limit.