The LieTorch library generalizes PyTorch to 3D transformation groups. Just as torch.Tensor is a multi-dimensional matrix of scalar elements, lietorch.SE3 is a multi-dimensional matrix of SE3 elements. We support common tensor manipulations such as indexing, reshaping, and broadcasting. Group operations can be composed into computation graphs and backpropagation is automatically peformed in the tangent space of each element. For more details, please see our paper: Tangent Space Backpropagation for 3D Transformation Groups Zachary Teed and Jia Deng, CVPR 2021