The reduction in its area resulted from an imperial decree dated 21 November 1808 and which established the neighbouring department of Tarn-et-Garonne, to the north.

Haute-Garonne is part of the current region of Occitanie and is surrounded by the departments of Hautes-Pyrénées, Gers, Tarn-et-Garonne, Tarn, Aude, and Ariège.

The department is crossed by the upper course of the Garonne river (hence the name) for nearly 200 kilometers (120 mi).

The Garonne enters France from Spain at the town of Fos, and goes through Toulouse and leaves the department.

The highest elevation is the Peak of Perdiguère, at 3,222 meters (10,571 feet) above sea level.

As of 2019, there were eight communes with more than 15,000 inhabitants:[3] This department was the political base of former Prime Minister Lionel Jospin.