The Virtual Observatory (VO) is a collective term for the technologies and mechanisms that aim to provide seamless access to astronomical datasets around the world - something like the world wide web but for astronomical data. In practice it is an evolving set of standards for data centers to expose their data so that it can be located, downloaded, interacted with, and understood by VO-aware tools such as TOPCAT, Aladin and ESASky, as well as by code in scientist-friendly languages like Python.

Much existing and future data (Gaia, LSST, Euclid and many smaller projects) is or will be made available through VO interfaces - as the interfaces become better integrated into software, users may not even be aware of this.

Bristol has a long history of involvement with the International Virtual Observatory Alliance (IVOA), the body that oversees VO development, and continues to be active in authoring VO standards and providing validation infrastructure for VO services, as well as developing one of the most prominent VO user tools, TOPCAT.