Web GIS, also known as Web-based GIS, are Geographic Information Systems (GIS) that employ the World Wide Web (the Web) to facilitate the storage, visualization, analysis, and distribution of spatial information over the Internet. Web GIS involves using the Web to facilitate GIS tasks traditionally done on a desktop computer, as well as enabling the sharing of maps and spatial data.

Web GIS is a subset of Internet GIS, which is itself a subset of distributed GIS. The most common application of Web GIS is Web mapping, so much so that the two terms are often used interchangeably in much the same way as between digital mapping and GIS. However, Web GIS and web mapping are distinct concepts, with web mapping not necessarily requiring a Web GIS.

The use of the Web has dramatically increased the effectiveness of both accessing and distributing spatial data, two of the most significant challenges of desktop GIS. Many functions, such as interactivity, and dynamic scaling, are made widely available to end users by web services. The scale of the Web can sometimes make finding quality and reliable data a challenge for GIS professionals and end users, with a significant amount of low-quality, poorly organized, or poorly sourced material available for public consumption. This can make finding spatial data a time consuming activity for GIS users.

The history of Web GIS is very closely tied to the history of geographic information systems, Digital mapping, and the World Wide Web or the Web. The Web was first created in 1990, and the first major web mapping program capable of distributed map creation appeared shortly after in 1993. This software, named PARC Map Viewer, was unique in that it facilitated dynamic user map generation, rather than static images. This software also allowed users to employ GIS without having it locally installed on their machine. The US federal government made the TIGER Mapping Service available to the public in 1995, which facilitated desktop and Web GIS by hosting US boundary data. In 1996, MapQuest became available to the public, facilitating navigation and trip planning, which quickly became a major utility on the early Web.

In 1997, Esri began to focus on their desktop GIS software, which in 2000 became ArcGIS. This led to Esri dominating the GIS industry for the next several years. In 2000 Esri launched the Geography Network, which offered some web GIS functions. In 2014, ArcGIS Online replaced this, and offers significant Web GIS functions including hosting, manipulating, and visualizing data in dynamic applications.

Web GIS has numerous applications and functions and manages most distributed spatial information. Diverse industries and disciplines, including mathematics, history, business and education can all leverage Web GIS to integrate geographic approaches to data.

The United States Census Department extensively uses Web GIS to distribute its boundary data, such as TIGER files, and demographics to the public. The "2020 Census Demographic Data Map Viewer" runs on an ESRI Web Map Application, and provides demographic information, such as population, race, and housing information at the state, county, and census tract levels.

Literature has identified educational benefits and applications of Web GIS at the elementary, primary, and university levels of education. Using story maps and dashboards allows for new ways of displaying spatial data, and facilitates student interaction. As Web GIS tools are often user friendly, teachers can create their own visualizations for the classroom, or even have students make their own to teach geographic concepts.