The Chahamanas of Shakambhari (IAST: Cāhamāna), colloquially known as the Chauhans of Sambhar or Chauhans of Ajmer, were an Indian dynasty that ruled parts of present-day Rajasthan and neighbouring areas between the sixth and twelfth centuries in the Indian subcontinent. The territory ruled by them was known as Sapadalaksha. They were the most prominent ruling family of the Chauhan Rajput clan.

The Chahamanas originally had their capital at Shakambhari (present-day Sambhar Lake Town). Until the 10th century, they ruled as Pratihara vassals. When the Pratihara power declined after the Tripartite Struggle, the Chahamana ruler Simharaja assumed the title Maharajadhiraja. In the early 12th century, Ajayaraja II moved the kingdom's capital to Ajayameru (modern Ajmer). For this reason, the Chahamana rulers are also known as the "Chauhans of Ajmer".

The Chahamanas fought several wars with their neighbours, including the Chaulukyas of Gujarat, the Tomaras of Delhi, the Paramaras of Malwa and the Chandelas of Bundelkhand. From 11th century onwards, they started facing Muslim invasions, first by the Ghaznavids, and then by the Ghurids. The Chahamana kingdom reached its zenith under Vigraharaja IV in the mid-12th century. The dynasty's power effectively ended in 1192 CE, when the Ghurid invader Muhammad of Ghor defeated and executed Vigraharaja IV's nephew Prithviraj Chauhan.

According to the 1170 CE Bijolia rock inscription of Someshvara, the early Chahamana king Samantaraja was born at Ahichchhatrapura in the gotra of sage Vatsa. Historian R. B. Singh theorizes that the Chahamanas probably started out as petty rulers of Ahichchhatrapura (identified with Nagaur), and moved their capital to Shakambhari (Sambhar) as their kingdom grew. Later, they became the vassals of the Imperial Pratiharas.

Several mythical accounts of the dynasty's origin also exist. The earliest of the dynasty's inscriptions and literary works state that the dynasty's progenitor was a legendary hero named Chahamana. They variously state that this hero was born from Indra's eye, in the lineage of the sage Vatsa, in the solar dynasty and/or during a ritual sacrifice performed by Brahma. A popular medieval account classifies the dynasty among the four Agnivanshi clans, whose ancestors are said to have come out of sacrificial fire pit. The earliest sources to mention this legend are the 16th century recensions of Prithviraj Raso. Some colonial-era historians interpreted this myth to suggest a foreign origin of the dynasty, speculating that the foreign warriors were initiated into the Hindu society through a fire ritual. However, the earliest extant copy of Prithviraj Raso does not mention this legend at all. Instead, it states that the first ruler of the dynasty was Manikya Rai, who is said to have been born from Brahma's sacrifice.

The core territory of the Chahamanas was located in present-day Rajasthan. It was known as Sapadalaksha (IAST: Sapādalakṣa) or Jangala-desha (IAST: Jangaladeśa).

The term Jangladesha ("rough and arid country") appears to be older, as it mentioned in the Mahabharata. The text does not mention the exact location of the region. The later Sanskrit texts, such as Bhava Prakasha and Shabdakalpadruma Kosha suggest that it was a hot, arid region, where trees requiring little water grew. The region is identified with the area around Bikaner.

The term Sapadalaksha (literally "one and a quarter lakhs" or 125,000) refers to the large number of villages in the area. It became prominent during the Chahamana reign. It appears that the term originally referred to the area around modern Nagaur near Bikaner. This area was known as Savalak (vernacular form of Sapadalaksha) in as late as 20th century. The early Chahamana king Samantaraja was based in Ahichchhatrapura, which can be identified with modern Nagaur. The ancient name of Nagaur was Nagapura, which means "the city of the serpent". Ahichchhatrapura has a similar meaning: "the city whose chhatra or protector is serpent".