The Lahaul and Spiti district in the Indian state of Himachal Pradesh consists of the two formerly separate districts of Lahaul () and Spiti (; or ). The present administrative center is Kyelang in Lahaul. Before the two districts were merged, Kardang was the capital of Lahaul, and Dhankar the capital of Spiti. The district was formed in 1960 and is the fourth least populous district in India (out of 640). It is the least densely populated district of India, according to the Census of India 2011.
Geologically located in the Himalayas and the Tibetan Plateau, Lahaul and Spiti district is connected to Manali through the Rohtang Pass. Kunzum la or the Kunzum Pass (altitude ) is the entrance pass to the Spiti Valley from Lahaul. It is from Chandra Tal. To the south, Spiti ends from Tabo, at the Sumdo where the road enters Kinnaur and joins National Highway 5.
Spiti is barren and difficult to cross, with an average elevation of the valley floor of . It is surrounded by lofty ranges, with the Spiti River rushing out of a gorge in the southeast to meet the Sutlej River. It is a typical mountain desert area with an average annual rainfall of only .
The district has close cultural links with Ngari Prefecture of Tibet Autonomous Region.
The harsh conditions of Lahaul permit only scattered tufts of hardy grasses and shrubs to grow, even below . Glacier lines are usually found at . Due to changes in climate, people in the Lahaul valley are able to grow some vegetables like cabbages, potatoes, green peas, radishes, tomatoes, carrots and leafy vegetables. The main cash crops are potatoes, cabbages, and green peas.
Some of the most common species of flora found in the Valley of Spiti include Cousinia thomsonii, Seseli trilobum, Crepis flexuosa, Caragana brevifolia and Krascheninnikovia ceratoides. There are over 62 species of medicinal plants found there as well.
Several species of juniper grow in the valley, noted for their adaptation to the cold desert climate conditions. They are used by local people for religious purposes and for subsistence.