The Palazzo della Ragione ("Palace of Reason") is a historic building of Milan, Italy, located in Piazza Mercanti, facing the Loggia degli Osii.

The structural changes were designed by architect Francesco Croce, who added a new upper floor with large round windows and restyled the whole building based on Neoclassic canons.

Other major modifications of the buildings were done in 1854 by architect Enrico Terzaghi; these included glass panes that closed the ground floor ambulatory, which was reopened between 1905 and 1907.

Between 1866 and 1870, the building housed the headquarters of the Banca Popolare di Milano, a major Milanese bank, but thereafter returned to its function as a legal archives seat until 1970.

In 1978, Marco Dezzi Bardeschi restored the building again, but he strongly opposed any proposal of structural change, including that of removing the upper floor added by Croce.