Archaeological discoveries show the existence of a people in the present-day Najaf dating back to the 1st century BC. Najaf possesses one of the largest burial grounds in the vicinity for Christians. Discoveries in the following centuries point toward the city's multicultural and diverse religious history. Mohammed al-Mayali, director of Inspectorate Effects of the province of Najaf, states, "the excavation on the graves, which we have been working on for years, confirm that "Najaf" contains the largest Christian cemetery in Iraq, with a cemetery area of 1416 acres. We have found indications of Christianity on the graves through representations of crosses and stones with Christ-like engravings. There are also relics that date back to the Sassanid period. Also discovered in the excavation was proof of a thriving glass industry. Pots were decorated with the cross, as well as Hebrew writings, indicating a community of religious coexistence."^{[citation needed]}

Wadi-us-Salaam in Najaf was once a holy cemetery for Jews and was then called Baniqia, which could be the first recorded name for the area.^{[19] [20]}

The name Baniqia also was found in some texts which state that Abraham once visited and stayed in this village before continuing his journey from Mesopotamia to Arabia.^[21][22]

In Islam, the city is considered to have started with Ali who instructed that his burial place should remain a secret, as he had many enemies and he feared that his body might be subjected to some indignity. According to legend, the body of Ali was placed on a camel which was driven from Kufah. The camel stopped a few miles west of the city where the body was secretly buried.^[23] No tomb was raised and nobody knew of the burial place except for a few trusted people. It is narrated that more than a hundred years later the Abbasid Caliph, Harun al-Rashid, went deer hunting outside Kufah, and the deer sought sanctuary at a place where the hounds would not pursue it. On inquiry as to why the place was a sanctuary, he was told that it was the burial place of ‘Ali. Harūn ar-Rashīd ordered a mausoleum to be built on the spot and in due course the town of Najaf grew around the mausoleum.^[24]

In early 14th century, Sheikh Ibn Battuta visited the burial site of Ali ibn Abi Talib during his travels in Iraq after his pilgrimage to Mecca. During this period, Najaf was called Meshhed Ali. As Translated by Samuel Lee, Ibn Battuta in his Arabic Rihla relates:^[25]

The Ottomans were expelled in an uprising in 1915, following which the city fell under the rule of the British Empire. The sheikhs of Najaf including Sayyed Mahdi Al-Awadi rebelled in 1918, killing the British governor of the city, and cutting off grain supplies to the Anazzah, a tribe allied with the British. In retaliation the British besieged the city and cut off its water supply. The rebellion was put down and the rule of the sheikhs was forcibly ended. A great number of the Shi‘i ‘Ulema’ were expelled into Persia, where they set the foundations for the rise of the city of Qom as the center of the Shi‘ite learning and authority, in lieu of Najaf. Najaf lost its religious primacy to Qom, and was not to regain it until the 21st century, during the establishment of a Shī‘ī-majority government in Iraq after 2003.

In the 20th century, much of the Old City was rebuilt in a series of modernization initiatives. Beginning in the 1950s, many historic buildings and monuments, including those adjoining the shrine, were demolished for the construction of Sadeq, Zainulabidin, Rasool and Tousi streets. In 1958, the city wall was torn down and replaced with a ring road. In the 1980s, the entire area between the shrine and the city's western edge was demolished, and the residents resettled outside the city, in what locals perceived as a government reprisal for the Shia uprising under the leadership of Muhammad Baqir al-Sadr, who was based in the neighborhood.^[29]

During the 2003 U.S. invasion of Iraq, Najaf was a key target of the invading United States Armed Forces. The city was encircled during heavy fighting on 26 March 2003 and was captured on 3 April 2003 (Battle of Najaf). The clerical authorities of the Shī‘ī enclave of Sadr City in Baghdad, which claimed autonomy in April 2003, after the fall of Baghdad, claimed to be taking their orders from senior clerics in Najaf.

On 4 April 2004, the Mahdi Army attacked the Spanish-Salvadoran-ALARNG base (Camp Golf, later renamed Camp Baker) in An Najaf, part of a coordinated uprising across central and southern Iraq in an apparent attempt to seize control of the country ahead of the 30 June 2004 handover of power to a new Iraqi government. This uprising led to the American troops arriving in the city in the wake of the Spanish withdrawal. In August 2004, heavy fighting broke out again between U.S. forces and Al-Sadr's Mahdi Army.^[30] The battle lasted three weeks and ended when senior Iraqi cleric Grand Ayatollah Ali al-Sistani negotiated an end to the battle.^[31]

In 2012, Najaf was named the Cultural Centre of the Arab World.^[32] On 6 March 2021, Pope Francis visited Najaf during his historic papal visit to Iraq and held an interfaith dialogue with al-Sistani, where he expressed a message of peaceful coexistence between Muslims and Christians in the country.^[33] During the ISIS war, Najaf Shiites launched solidarity initiative with Sunni areas affected by ISIS.^[34] Many Iraqis including religious minorities such as Christians from the north, as well as Lebanese Shia have found safe haven in the city.^[35][36]

Najaf has a hot desert climate, BWh in the Köppen climate classification, with long, very hot summers and mild winters. The average annual temperature is 23.6 °C (74.5 °F). The rainfall averages 69 mm (2.71 in).

Najaf being home to the Sanctuary of Imam Ali (considered the patriarch and the first of the Twelve Imams) is the destination of large numbers of Shi’i religious pilgrims annually hailing from around the world.

The city of Najaf is home to Al-Najaf SC and Naft Al-Wasat SC that play in the second tier Iraqi Premier Division League.

Najaf has two football stadiums, the An-Najaf Stadium (also referred to as the old stadium) with a capacity of 12,000 spectators, and the newer Al-Najaf International Stadium with a capacity of 30,000. The latter stadium is the home of the Stars League club Al-Najaf as well as Naft Al-Wasat, whilst the former is the home stadium of the neighbouring Al-Kufa SC.

Some of the universities located in Najaf include:

• Al-Furat Al-Awsat Technical University
• Islamic University College
• University of Alkafeel
• Jabir Ibn Hayyan Medical University
• Altoosi University College

The Hawza of Najaf has been a centre of traditional Shia Islamic education since the 11th century CE. It was possibly established in the 9th century CE, making it the oldest Shi’i seminary among those still active, and many prominent Shi’i Islamic scholars have studied in the Najaf Seminary, including Murtadha al-Ansari, and Ali al-Sistani.

As of 2024, Najaf has three sister cities:

• Minneapolis, United States^[65][66]
• Najafabad, Iran^[67]