Historically, Ajmer was earlier known as Ajayameru meaning ‘Invincible Mountain’. It was founded in the late 7th century A.D. by Shakambhari Chahamana (Chauhan) king Ajayaraja II (ruled c.?1110–1135 CE). During the 12th century, Prithviraj Chauhan (1149-1192 CE), the ruler of the Rajput Chauhan dynasty ruled Ajmer along with Delhi. In 1193, Ajmer was conquered by Muhammad of Ghor who founded Delhi Sultanate, in the same year. In 1365, Ajmer regained independence under the ruler of Mewar. In 1509, control of Ajmer was disputed between the Maharajas of Mewar and Marwar. Finally, Ajmer was conquered by Marwar in 1532. In 1553, the state was ruled by Hemu, who was killed in 1556 in the Second Battle of Panipat. In 1559, the city was conquered by Emperor Akbar in 1559. In the early 1700s, control passed to the Marathas. In 1818, the British forced the Marathas to cede the city for 50,000 rupees, whereupon it became part of the Province of Ajmer-Marwar in the colonial British Raj.

Historian Dasharatha Sharma notes that the earliest mention of the city's name occurs in Palha's Pattavali, which was copied in 1113 CE (1170 VS) at Dhara. This suggests that Ajmer was founded sometime before 1113 CE. A prashasti (eulogistic inscription), issued by Vigraharaja IV and found at Adhai Din Ka Jhonpra, states Ajayadeva (that is, Ajayaraja II) moved his residence to Ajmer. The later text Prabandha-Kosha states that it was the 8th century king Ajayaraja I who commissioned the Ajayameru fort, which later came to be known as the Taragarh fort of Ajmer. According to historian R. B. Singh, this claim appears to be true, as inscriptions dated to the 8th century CE have been found at Ajmer. Singh theorizes that Ajayaraja II later enlarged the town, constructed palaces, and moved the Chahamana capital from Shakambhari to Ajmer.

Bhanu Bharti (born in 1947) is a veteran Indian theatre director, choreographer, playwright and founder-director of Aaj Rangmandal theatre group. He was awarded with National Award for his contribution to the field of theatre and Sangeet Natak Akademi Award in the year 1997 for contribution in Dance Music and Drama. He was also honored with Rajasthan Sahitya Akademi Award and Rajasthan Sangeet Natak Akademi Award. Manohar Shyam Joshi (1933-2006) was a Hindi writer, journalist and scriptwriter from Ajmer. He got Sahitya Akademi Award for Kyap.

Geographically, Ajmer is the fifth largest city of Rajasthan. It lies at 26°45'N latitude, 74°64'E longitude and 486 m altitude. The district extends to a geographical area of 8,481 square kilometers and ranks 14th in the State and 90th in India on basis of this size. As per data recorded in the year 2021, there was a total 3.91% forest area of total geographical area. There is flat and broken portion in the East of the district. Aravalli Range lies in the western parts, from north-west to south-west. The district is the part of the Thar Desert. There is an artificial lake which is protected by the massive walls of the Nagpathar range or Serpent rock. The main river of the region is Banas River which runs through the South-Eastern boundary of the district. Sagarmati, Saraswati, Khari and Dai are the four small streams rivers which also pass through the district. The actual rainfall in the district was 596.5 mm in the year of 2021-22.

Administration wise, the district is divided into nine sub-districts. It has 11 towns and 1,111 villages. Hindi is its administrative language. The district of Ajmer came into existence on the November 1, 1956 in the state of Rajasthan with its district headquarters located at Ajmer which is located at a distance of 131 km. from the State Capital.

Demographically, the district has a total number of 4,83,931 households with a total population of 25,83,052 including 13,24,085 are males and 12,58,967 are females. The density of population of the district is 305 persons per sq km. The population growth rate during the period 2001 to 2011 was 18.40% including 17.18% were males and 19.70% were females. The sex ratio is pegged at 951 females for every 1000 males while child ratio stands 901 girls per 1000 boys. The schedule caste population of the district was recorded as 4,78,027 including 2,43,750 are males and 2,34,277 are females. The schedule tribe population was 63,482 including 32,408 are males and 31,074 are females. As per 2011 census the major religion in the district is Hindu and Muslim with 85.23% and 12.16% of the total population. According to 2011 census the principal language in the district is Hindi with 96.43.%. In the year 2020 the number of live births in the district was 74,055 out of which 38,576 were males and 35,472 were females. In the same year the number of deaths in the district was 24,429 out of which 14,558 were males and 9,869 were females.

In the year 2020-21 the gross domestic product in the district was Rs. 40,96,606 lakhs at current price and Rs. 26,79,298 lakhs at constant prices in the year 2011-2012. The net domestic product in the district during the period 2020-21 was Rs. 37,01,128 lakh at current price and Rs. 23,79,568 lakh at constant prices in the year 2011-2012. The Per Capita Income or NDDP, At Factor Cost during the period 2020-21 was Rs. 1,24,548 at current price and Rs. 80,076 at constant prices in the year 2011-2012. As per 2011 census the literacy rate in the district is 69.33% including 82.44% are males and 55.68% are females. Government Engineering College, Ajmer (ECA) is one of the engineering colleges in Rajasthan. It was established in the year 1997. Another engineering college is Government Mahila Engineering College, Ajmer, is said to be the first women engineering college in north India.

Har Bilas Sarda (1867-1955) was an academic, judge and politician. He is famous for having introduced the Child Marriage Restraint Act (1929). He was elected as a Member of the Central Legislative Assembly in January 1924 and was re-elected to the Assembly in 1926 and 1930. Neena Vikram Verma, born 19th October, 1960 in Ajmer, is an Indian politician. She belongs to Bharatiya Janata Party (BJP). She is a member of the Madhya Pradesh Legislative Assembly for Dhar Vidhan Sabha Constituency.

There are a number of historical and religious places which are great attraction for the tourists. During the year 2021, there were 4,232 foreign tourists and 66,26,171 domestic tourists who visited these places of the district. These places are Ana Sagar Lake, Taragarh, Pushkar Lake, Akbar's Palace and Museum, Bhagchand ki Kothi, Durga Bagh, Mayo College and Museum, Delhi Gate, Archaeological Museum, Rani Mahal, Foy Sagar Lake, Dargah Shariff, Shah Jahan's Mosque, Adhai-Din ka Jhonpra Mosque, and St. Mary's Graveyard.