LiDAR data processing is the basis of subsequent extensive applications. It aims to provide high-precision three-dimensional data or attribute information of targets for applications. In practice, the processing methods of LiDAR discrete point cloud data, full-waveform data, and photon-counting data are different due to the different detection and digitization methods. This chapter introduces the processing flows and key techniques for these three LiDAR data types in detail. The key steps of LiDAR discrete point cloud data processing include point cloud denoising, point cloud filtering, and point cloud classification. LiDAR full-waveform data processing steps involve waveform denoising, waveform decomposition, waveform deconvolution, and waveform characteristic parameter extraction. LiDAR photon-counting data processing steps involve photon-counting denoising and photon-counting classification.