FOSS4G is the acronym for Free and Open Source Software for Geospatial/ Geo Informatics, first coined in early 2004 by a research group working on I18N of GRASS and MapServer. Free and open-source software (FOSS) is software where anyone is allowed usage (use, copy, study, and change) of licensed software in any way. The source code is openly shared to encourage people to come up with improved design for the software.

The OSGeo Conference Committee is the steadying factor of FOSS4G over the years. Organization of FOSS4G starts roughly 2 years in advance as the venue rotates around the world when a call for bids is sent out.