The Thar or Great Indian Desert, an arid sandy region in the north-west of India lying largely in western Rajasthan, west of the Aravalli Range.
- Lies mainly in Rajasthan and extends into Gujarat, Punjab, and Haryana, and across the border into Pakistan; it is the world's most densely populated desert.
- Receives less than about 150 mm of rain a year; the climate is hot and dry with high diurnal and seasonal temperature ranges.
- The Aravalli Range lies parallel to the path of the south-west monsoon and so fails to obstruct or lift the moisture-bearing winds, which is one reason the region stays arid.
- Landforms include sand dunes (barchans and longitudinal dunes), inland drainage, and ephemeral streams; the Luni is the only sizeable river, ending in the Rann of Kutch.
- The Indira Gandhi Canal (Rajasthan Canal), drawing Sutlej-Beas water, has greened parts of the desert for agriculture.
The location relative to the Aravallis, the rain-shadow style aridity, the Luni river, the Indira Gandhi Canal, and the security significance of the Rajasthan-Gujarat desert frontier (BSF deployment) are recurring facts.
The Aravallis do not block the monsoon because they run roughly parallel to the wind direction; the Luni is the only major river and drains into the Rann of Kutch, not to the sea proper.
Arid Thar Desert of western Rajasthan, under 150 mm rain, the Luni its only river, greened in parts by the Indira Gandhi Canal.