Neurodegenerative diseases (NDs) pose clinical challenges due to their complexity and molecular heterogeneity. Here, we present a pan-neurodegeneration atlas (PanNDA) from multilayer, deep proteomic analysis of 2,279 human brain samples spanning 6 major NDs: Alzheimer's disease (AD), Lewy body dementia (LBD), frontotemporal lobar degeneration with TDP-43 pathology, progressive supranuclear palsy with tau pathology, vascular dementia, and Parkinson's disease. PanNDA integrates data from whole proteome, detergent-insoluble proteome, and posttranslational modifications (phosphorylation and ubiquitination), enabling intra- and inter-disease comparisons. Intra-disease analyses uncover distinct molecular subtypes (e.g., three in AD and four in LBD), reveal dysregulated pathways, and prioritize top-ranked proteins. Inter-disease comparisons identify shared alterations in NDs, such as GPNMB in microglial and lysosomal activation and NPTX2 in synaptic regulation, alongside disease-specific changes and hub regulators within protein networks. Overall, PanNDA provides a systems-level framework for understanding ND mechanisms and serves as a foundational resource that is accessible via an interactive website: https://penglab.shinyapps.io/pannda.