Title: Memory Efficient Dynamic Sparse Training. Abstract: The excessive memory and energy consumption of modern Artificial Neural Networks (ANNs) is posing limitations on the machines that can run these models. Sparsification of ANNs is often motivated by time, memory and energy savings only during model inference, yielding no benefits during training. A growing body of work is now focusing on providing the benefits of model sparsification also during training. While these methods improve the energy efficiency during training, the algorithms yielding the most accurate models still have a peak memory usage on the same order as the dense model. We propose a Dynamic Sparse Training (DST) algorithm that reduces the peak memory usage during training while preserving the energy advantages of sparsely trained models. We evaluate our algorithm on CIFAR-10/100 using ResNet-56 and VGG-16 and compare it against a range of sparsification methods. The benefits of our method are twofold: first, it allows for a given model to be trained to an accuracy on par with the dense model while requiring significantly less memory and energy; second, the savings in memory and energy can be allocated towards training an even larger sparse model on the same machine, generally improving the accuracy of the model.