Three-dimensional neural network array. In an exemplary embodiment, a three-dimensional (3D) neural network includes a plurality of input conductors forming a plurality of stacked input layers having a first orientation, and at least one output conductor forming an output layer having the first orientation. The three-dimensional (3D) neural network also includes a plurality of hidden conductors having a second orientation. Each hidden conductor includes an in-line threshold element. The three-dimensional (3D) neural network also includes synapse elements coupled between the hidden conductors and the input conductors and between the hidden conductors and the output conductor. Each synapse element includes a programmable resistive element.