pymatgen (Python Materials Genomics) is a robust, open-source Python library for materials analysis, primarily used for high-throughput computational materials science. It provides core object representations for crystal structures, molecules, and computational outputs (VASP, Q-Chem, Gaussian, etc.), and extends into analysis modules for phase diagrams, battery electrodes, coordination environments, magnetism, elasticity, surface science, diffraction, and spectroscopy. The library powers the Materials Project database and includes CLI tools for structure manipulation, POTCAR generation, and plotting. It features extensive use of MSONable serialization, abstract base classes, and a correction scheme pattern for DFT energy adjustments. While heavily integrated with the Materials Project ecosystem, its modular design allows reuse of individual analysis components in other materials research pipelines.