Great Seljuk architecture, or simply Seljuk architecture, refers to building activity that took place under the Great Seljuk Empire (11th–12th centuries). The developments of this period contributed significantly to the architecture of Iran, the architecture of Central Asia, and that of nearby regions. It introduced innovations such as the symmetrical four-iwan layout in mosques, advancements in dome construction, early use of muqarnas, and the first widespread creation of state-sponsored madrasas. Their buildings were generally constructed in brick, with decoration created using brickwork, tiles, and carved stucco.

The Seljuk Turks created the Great Seljuk Empire in the 11th century, conquering all of Iran and other extensive territories from the Hindu Kush to eastern Anatolia and from Central Asia to the Persian Gulf. In 1050 Isfahan was established as capital of the Great Seljuk Empire under Alp Arslan. In 1071, following the Seljuk victory over the Byzantine Empire at the Battle of Manzikert, Anatolia was opened up to Turkic settlers. The center of Seljuk architectural patronage was Iran, where the first permanent Seljuk edifices were constructed. The cultural apogee of the Great Seljuk state is associated with the reign of Malik-Shah I (r. 1072–1092) and the tenure of Nizam al-Mulk as his vizier. Among other policies, Nizam al-Mulk championed Sunnism over Shiism and founded a network of madrasas as an instrument for this policy. This marked the beginning of the madrasa as an institution that spread across the Sunni Islamic world. Although no Seljuk madrasas have been preserved intact today, the architectural design of Seljuk madrasas in Iran likely influenced the design of madrasas elsewhere.

While the apogee of the Great Seljuks was short-lived, it represents a major benchmark in the history of Islamic art and architecture in the region of Greater Iran, inaugurating an expansion of patronage and of artistic forms. Much of the Seljuk architectural heritage was destroyed as a result of the Mongol invasions in the 13th century. Nonetheless, compared to pre-Seljuk Iran, a much greater volume of surviving monuments and artifacts from the Seljuk period has allowed scholars to study the arts of this era in much greater depth than preceding periods. The period of the 11th to 13th centuries is also considered a "classical era" of Central Asian architecture, marked by a high quality of construction and decoration. Here the Seljuk capital was Merv, which remained the artistic center of the region during this period. The region of Transoxiana, north of the Oxus, was ruled by the Qarakhanids, a rival Turkic dynasty who became vassals of the Seljuks during Malik-Shah's reign. This dynasty also contributed to the flourishing of architecture in Central Asia at this time, building in a style very similar to the Seljuks. Similarly, to the east of the Great Seljuk Empire the Ghaznavids and their successors, the Ghurids, built in a closely related style. A general tradition of architecture was thus shared across most of the eastern Islamic world (Iran, Central Asia, and parts of the northern Indian subcontinent) throughout the Seljuk period and its decline, from the 11th to 13th centuries.

After the decline of the Great Seljuks in the late 12th century various Turkic dynasties formed smaller states and empires. A branch of the Seljuk dynasty ruled a Sultanate in Anatolia (also known as the Anatolian Seljuks or Seljuks of Rum), the Zengids and Artuqids ruled in Upper Mesopotomia (known as al-Jazira) and nearby regions, and the Khwarazmian Empire ruled over Iran and Central Asia until the Mongol invasions of the 13th century. Under Zengid and Artuqid rule, the cities of Upper Mesopotamia became important centers of architectural development that influenced the wider region. Zengid rule in Syria also helped to spread architectural forms from the eastern Islamic world to this region. In Anatolia, the Seljuks of Rum oversaw the construction of monuments reflecting a diverse array of influences, drawing on both the eastern Islamic world and on more local Byzantine, Armenian, and Georgian sources.

The most important religious monument from the Great Seljuk period is the Jameh Mosque of Isfahan, which was expanded and modified by various Seljuk patrons in the late 11th century and early 12th century. Two major and innovative domed chambers were added to it in the late 11th century: the south dome (in front of the mihrab) was commissioned by Nizam al-Mulk in 1086–87 and the north dome was commissioned by Taj al-Mulk in 1088–89. Four large iwans were later erected around the courtyard around the early 12th century, giving rise to the four-iwan plan. These additions constitute some of the most important architectural innovations of the Seljuk period.

The four-iwan plan already had roots in ancient Iranian architecture and has been found in some Parthian and Sasanian palaces. Soon after or around the same time as the Seljuk work in Isfahan, it appeared in other mosques such as the Jameh Mosque of Zavareh (built circa 1135–1136) and the Jameh Mosque of Ardestan (renovated by a Seljuk vizier in 1158–1160). It subsequently became the "classic" form of Iranian Friday (Jameh) mosques.

The transformation of the space in front of the mihrab (or the maqsura) into a monumental domed hall also proved to be influential, becoming a common feature of future Iranian and Central Asian mosques. It also features in later mosques in Egypt, Anatolia, and beyond. Both of the domes added to the Isfahan mosque also employ a new type of squinch consisting of a barrel vault above a pair of quarter-domes, which was related to early muqarnas forms. The north dome of the Isfahan mosque, in particular, is considered a masterpiece of medieval Iranian architecture, with the interlacing ribs of the dome and the vertically aligned elements of the supporting walls achieving a great elegance.

Another innovation by the Seljuks was the "kiosk mosque".^{[additional citation(s) needed]} This usually small edifice is characterised by an unusual plan consisting of a domed hall, standing on arches with three open sides giving it the kiosk character. Furthermore, the minarets constructed by the Seljuks took a new dimension adopting an Iranian preference of cylindrical form featuring elaborate patterns. This style was substantially different from the typical square shaped North African minarets.