PeptideAtlasPeptideAtlas is a multi-organism, publicly accessible compendium of peptides identified from a large collection of tandem mass spectrometry proteomics experiments. It aggregates raw mass spectrometry outputs across species (human, mouse, yeast, etc.), searches them with current search engines and protein sequences, and processes results through the Trans Proteomic Pipeline to assign uniform probabilities and false discovery rates. It offers browseable/searchable data, downloadable raw data and search results, and provides various organism-specific builds and tools like THISP and ProteoMapper for querying and analysis.