The Earthquake Catalog Repository and Viewer is a community-oriented, curated collection of earthquake catalogs developed within the CRESCENT cyberinfrastructure framework to support research, visualization, and analysis of seismicity. The repository standardizes diverse earthquake catalogs into a consistent, machine-readable format, enabling interoperability, reproducibility, and transparent comparison across datasets. The accompanying interactive web-based Earthquake Catalog Viewer (https://eqcat.cascadiaquakes.org) allows users to explore, visualize, and compare catalog data in real time. Comprehensive documentation, metadata standards, and submission guidelines are provided in the project’s Jupyter Book (https://cascadiaquakes.github.io/earthquake_catalog_repository/), which also describes the structure and provenance of included catalogs. By integrating standardized data curation with interactive visualization tools, this resource facilitates community contribution and broadens access to high-quality earthquake catalog data for scientific research, hazard analysis, and education.