Marischal College (/ˈmɑːrʃl/ MAR-shəl) is a large granite building on Broad Street in the centre of Aberdeen in north-east Scotland, and since 2011 has been the headquarters of Aberdeen City Council. The building was constructed for and is on long-term lease from the University of Aberdeen, which still uses parts of the building to store its museum collections. Today, it provides corporate office space and public access to council services, adjacent to the Town House, the city's historic seat of local government. It is the second largest granite building in the world.

The construction of the modern college building began in 1835, following the demolition of previous buildings on the site, and was completed in its present form in the early 1900s. Formerly the seat of the Marischal College and University of Aberdeen founded in 1593, the building was retained by the unified University of Aberdeen, which was created in 1860 by the merger of Marischal College and King's College. The buildings of Marischal College continued to be used for academic purposes until the mid-20th century and less and less until the early 2000s. During this period they were frequently rebuilt and expanded upon.

In the mid-to-late 20th century, teaching and academic activities at the university began to move to King's College or Foresterhill (for students of medicine) and by the early 21st century a new purpose for Marischal College was required. After a number of unsuccessful proposals, the majority of the building was leased to Aberdeen City Council to be restored and refurbished as office accommodation. The extensive renovation was completed on schedule and significantly under budget and the building opened to the public in June 2011. The university has retained the Mitchell Hall and a number of other significant parts of the building for its own use, in addition to its museum stores (formerly the Marischal Museum).

"Marischal College and University of Aberdeen" was the formal name of the former university which occupied the present Marischal College site then in New Aberdeen. The College was founded in 1593 by George Keith, 5th Earl Marischal of Scotland. The original charter of the university was lost by the early 18th century, but two near-contemporary copies exist – one of which was accepted by the courts in 1756 as being authentic. In this charter, Marischal College is described variously as a gymnasium, collegium (college), academia (academy) and universitas (university).

Marischal was the second of Scotland's post-medieval "civic universities", following the University of Edinburgh, created without Papal bull and with a more modern structure and a greater resemblance to the Protestant arts colleges of continental Europe. As such, both Edinburgh and Marischal came to be known as the "Town Colleges" of their respective cities. The university was founded with the expressed aim of training clergy for the post-Reformation Kirk. Its Greek motto translates as "virtue is self-sufficient".

The College was constructed on the site of a medieval Franciscan friary, disused after the Reformation. This building was later replaced by a William Adam-designed building in the mid-18th century; however, this, together with the friary remains, were demolished entirely for the construction of the present building between 1835 and 1906, as was the Longacre home of Bishop John Skinner, site of the 1784 consecration of Samuel Seabury, now marked by a plaque on the east wall of the College's quadrangle.

James Clerk Maxwell FRS, FRSE (1831–1879), described as "the most famous and influential professor Aberdeen has ever had" was appointed as Professor of Natural Philosophy in 1856 and continued in that post until the merger of Marischal College with King's College.

The Mitchell Hall, where University of Aberdeen graduations previously took place, was built in the early 20th century. It is named after Dr Charles Mitchell, an alumnus of the university and a Tyneside shipbuilder. A large stained-glass window dominates the hall, executed by TR Spence of London and representing the university's history.

The building was commended by poet John Betjeman following a visit to Aberdeen in 1947:

"No-one can dismiss Marischal College, Aberdeen, when looking at the work of the present century. Wedged behind a huge town hall in an expensive and attractive mid-Victorian baronial style, I saw a cluster of silver-white pinnacles. I turned down a lane towards them, the front broadened out. Oh! Bigger than any cathedral, tower on tower, forests of pinnacles, a group of palatial buildings rivalled only by the Houses of Parliament at Westminster.

"This was the famous Marischal College. Imagine the Victorian tower with a spire on top, and all that well-grouped architecture below of lesser towers, and lines of pinnacles executed in the hardest white Kemnay granite and looking out over the grey-green North Sea and you have some idea of the first impression this gigantic building creates.

"It rises on top of a simple Gothic one designed by Simpson in 1840. But all these spires and towers and pinnacles are the work of this century and were designed by Sir Alexander Marshall Mackenzie. You have to see them to believe them."

There is an urban legend of unknown origin that Marischal College was Adolf Hitler's favourite building in the United Kingdom and that he would have liked to use it as a residence if the outcome of the Second World War had been different.

The University of Aberdeen was created after the merger of Marischal College and King's College, Aberdeen in 1860 under the terms of the Universities (Scotland) Act 1858.

The following extract refers to this merger:

Universities of Kings College and Marischal College, Aberdeen. First Report of the Commissioners, 1838. 1837–38. Vol. XXXIII, 75p. [123] Chairman: Lord John Cunninghame.

The commissioners were in favour of a merger of the two colleges despite opposition from Kings College. They considered the unification as essential for the educational system of Northern Scotland although they disagreed with the proposed method of merger laid down by the last commission. The buildings of Marischal College were in very bad repair but new ones were under construction. Additions had been made in 1827 to Kings College buildings which were in a tolerable state of repair.

Throughout the 20th century, Marischall college housed all sciences and medicine. Since about 1960, the college housed the Department of Molecular and Cell Biology and Medical school.

The building standing today, which replaced a number of older structures, was constructed between 1837 and 1844 by Aberdeen architect Archibald Simpson. This 1837 building formed a U-shaped quadrangle, with a small entrance via an archway amidst unrelated housing on the west side. The building was substantially extended between 1893 and 1905 by Alexander Marshall Mackenzie, and with its new "granite cage" front, enclosing the quadrangle, it became the second-largest granite building in the world (exceeded only by the Escorial Palace near Madrid).