A Gantt chart is a bar chart that illustrates a project schedule. It was designed and popularized by Henry Gantt c. 1910–1915. Modern Gantt charts also show the dependency relationships between activities and the current schedule status.

A Gantt chart is a type of bar chart that illustrates a project schedule. This chart lists the tasks to be performed on the vertical axis, and time intervals on the horizontal axis. The width of the horizontal bars in the graph shows the duration of each activity. Gantt charts illustrate the start and finish dates of the terminal elements and summary elements of a project. Terminal elements and summary elements constitute the work breakdown structure of the project. Modern Gantt charts also show the dependency (i.e., precedence network) relationships between activities. Gantt charts can be used to show current schedule status using percent-complete shadings and a vertical "TODAY" line.

Gantt charts are sometimes equated with bar charts.

Gantt charts are usually created initially using an early start time approach, where each task is scheduled to start immediately when its prerequisites are complete. This method maximizes the float time available for all tasks.

Widely used in project planning in the present day, Gantt charts were considered revolutionary when introduced. The first known tool of this type was developed in 1896 by Karol Adamiecki, who called it a harmonogram. Adamiecki, however, published his chart only in Russian and Polish which limited both its adoption and recognition of his authorship.

In 1912, Hermann Schürch [de] published what could be considered Gantt charts while discussing a construction project. Charts of the type published by Schürch appear to have been in common use in Germany at the time; however, the prior development leading to Schürch's work is unclear. Unlike later Gantt charts, Schürch's charts did not display interdependencies, leaving them to be inferred by the reader. These were also static representations of a planned schedule.

The chart is named after Henry Gantt (1861–1919), who designed his chart around the years 1910–1915. Gantt originally created his tool for systematic, routine operations. He designed this visualization tool to more easily measure productivity levels of employees and gauge which employees were under- or over-performing. Gantt also frequently included graphics and other visual indicators in his charts to track performance.

One of the first major applications of Gantt charts was by the United States during World War I, at the instigation of General William Crozier.