Regnellianum, named for its benefactor Anders Fredrik Regnell, is located in the corner of Trädgårdsgatan and Slottsgränd, adjacent to Östgöta Nation.

The building was constructed in 1891-92 following a donation from Anders Fredrik Regnell, a physician. In 1877, he was appointed doctor honoris causa (honorary doctor) at the Uppsala University jubilee party.

The Regnellianum was utilized by Uppsala University until 1968, serving as the offices of the Departments of Physiology and Pathology.

In 1981-1982, a major reconstruction was conducted to better meet the requirements of the Department of Theology.

At the dawn of the 21st century, the Department of Theology left the premises, and Regnellianum was let as a commercial office. Today, the building houses the Dag Hammarskjöld Library and the Law Library.

Regnellianum is a listed building in Sweden, meaning that it is legally protected due to its historical significance.