Ghazni (Pashto: غزني, Dari: غزنی), historically known as Ghaznayn (Pashto, Dari: غزنين) or Ghazna (Pashto, Dari: غزنه), also transliterated as Ghuznee, and anciently known as Alexandria in Opiana (Greek: Αλεξάνδρεια Ωπιανή), is a city in southeastern Afghanistan with a population of around 190,000 people. The city is strategically located along Highway 1, which follows the path that has served as the main road between Kabul and Kandahar for thousands of years. Situated on a plateau at 2,219 metres (7,280 ft) above sea level, the city is 150 kilometres (93 mi) south of Kabul and is the capital of Ghazni Province. The name Ghazni derives from the Persian word ganj, meaning "treasure."

Ghazni Citadel, the Minarets of Ghazni, the Palace of Sultan Mas'ud III, and several other cultural heritage sites have brought travelers and archeologists to the city for centuries. During the pre-Islamic period, the area was inhabited by various tribes who practiced different religions including Zoroastrianism, Buddhism and Hinduism. Arab Muslims introduced Islam to Ghazni in the 7th century and were followed in the 9th century by the Saffarids. Sabuktigin made Ghazni the capital of the Ghaznavid Empire in the 10th century. The city was destroyed by one of the Ghurid rulers but later rebuilt. It fell to several regional powers, including the Timurids and the Delhi Sultanate until it became part of the Hotaki dynasty, which was followed by the Durrani Empire or modern Afghanistan. During the First Anglo-Afghan War in the 19th century, the fortifications of Ghazni were partially demolished by British Indian forces.

In August 2018, the city became the site of the Battle of Ghazni with the Taliban briefly occupying it and taking control of most of the surrounding area. On 12 August 2021, the city was captured by the Taliban as part of the 2021 Taliban offensive.

In 2013, ISESCO declared Ghazni the year's Islamic Capital of Culture.

The city was founded some time in antiquity as a small market town. In the 6th century BCE, it was conquered by the Achaemenid king Cyrus II and incorporated into the Persian Empire. The city was subsequently incorporated into the empire of Alexander the Great in 329 BCE, and called Alexandria in Opiana. Ghazni may be the Gazaca (Gázaca or Gāzaca) mentioned by Ptolemy in the 2nd century. Following the fall of the Greco-Bactrian kingdoms, the region emerged as the heart of Zabulistan, a prosperous kingdom that controlled the trade routes between India, Iran, and Central Asia. From the 5th to the 7th centuries, Zabulistan was ruled by the Nezak Huns, whose rulers are famous for their distinctive gold coins depicting them with a bull's head crown. Under their rule, the area became a major center of Buddhism, as well as Zoroastrianism and Hinduism. It was this wealthy kingdom that the Chinese pilgrim Xuanzang visited in 644, describing a city named Jaguda—which was almost certainly the contemporary name of the later Ghazni.

"The country of Jāguda is more than seven thousand li in circuit, and its capital city, named Hexina (Ghazni), is over thirty li in circuit; but the capital is sometimes located in the city of Hesaluo (Guzar), which is also over thirty li in circuit, both cities being strongly fortified in invulnerable positions. The mountains and valleys are rich in natural resources, and the cultivated farmlands, divided by ridges, are high and dry. Crops are sown in proper seasons. Winter wheat is abundant, and vegetation is luxuriant with profuse flowers and fruits. The soil is good for growing aromatic turmeric, and it produces the hingu herb (Ferula asafoetida), which grows in the Rama-Indu Valley. In the city of Hesaluo there are gushing springs, the water of which flows to all sides, and the people make use of it for irrigation. The climate is severely cold with much frost and snow." - Xuanzang, 644 CE

In 683, Arab armies brought Islam to the region. From 680 to 870, the Zunbils were present in the area, and at times had their capital in Ghazni. Yaqub Saffari from Zaranj conquered the Zunbils in the late 9th century. The Saffarids reduced the formerly Lawik dynasty to tributary status. In 962, the Turkic slave commander of the Samanid Empire, Alp-Tegin, attacked the city and besieged the Citadel of Ghazni for four months, wresting the city from Abu Bakr Lawik. Around 965, Abu Bakr Lawik recaptured Ghazni from Alp-Tegin's son, Abu Ishaq Ibrahim, forcing him to flee to Bukhara. However, this was not to last long because Abu Ishaq Ibrahim shortly returned to the town with Samanid aid, and took control of the town once again. For nearly two hundred years (977–1163), the city was the dazzling capital of the Ghaznavid Empire, which encompassed much of what is today Afghanistan, Turkmenistan, Pakistan, Eastern Iran and Rajasthan. The Ghaznavids took Islam to India and returned with fabulous riches looted from Hindu temples. Although the city was sacked in 1151 by the Ghorid Ala'uddin, it became their secondary capital in 1173, and subsequently flourished once again. Between 1215 and 1221, Ghazni was ruled by the Khwarezmid Empire, during which time it was destroyed by the Mongol armies of Genghis Khan's son Ögedei Khan.

In the first decades of the 11th century, Ghazni was the most important center of Persian literature. This was the result of the cultural policy of Sultan Mahmud (reigned 998–1030), who assembled a circle of scholars, philosophers, and poets around his throne in support of his claim to royal status in Iran.