Gammapy: An open-source Python package for gamma-ray astronomy. Gammapy is a community-developed, open-source Python package for gamma-ray astronomy. It is an in-development affiliated package of Astropy that builds on the core scientific Python stack to provide tools to simulate and analyse the gamma-ray sky for telescopes such as CTA, H.E.S.S., VERITAS, MAGIC, HAWC and Fermi-LAT. Gammapy is a place for Python-coding gamma-ray astronomers to share their code and collaborate. Likelihood fitting of the morphology and spectrum of gamma-ray sources (using Sherpa), including multi-mission joint likelihood analysis and physical SED modeling (using Naima) is one important feature we’re working on. But Gammapy has a broader scope, we currently have code e.g. for data handling, background modeling, source detection, easy access to commonly used datasets and catalogs, statistical methods, even simulating Galactic source populations.