The origins of the building go back to Longobard times, to the 8th century, when on this site an oratory of San Michele in Orto was erected. It is first documented in 895, and was demolished in 1239. In its place Arnolfo di Cambia built, around 1290, a loggia for the sale of grain. From a place of commerce it soon became a place of devotion, and miracles were attributed to an image of the Virgin painted on a pillar.

In 1304 a fire severely damaged the loggia. In 1337 the Silk Guild commissioned a new loggia, finished in 1349, from the architects Neri di Fioravante, Benci di Cione and Francesco Talenti.
Meanwhile the image of the Virgin had faded and was replaced by Bernardo Daddi’s Madonna and Child (1346), known as the Madonna delle Grazie, still in situs, before which public and private oaths were sworn.
Devotion towards the image increased, especially after some miraculous cures during the terrible Plague of 1348. Probably conceived as an ex-voto, the monumental marble altar with Virtues and scenes from the life of the Virgin in relief, was commissioned a year after the Plague from Andrea di Cione, known as Orcagna, but not finished until 1359: a frame worthy of the Madonna delle Grazie. By now the loggia could no longer be regarded as a suitable place for a market, which was moved elsewhere at least by 1357.
In 1380 the building, which had always fulfilled both a civic and a religious function, had two upper storeys added onto it so that it could be used as a granary. Chutes for the wheat are still to be seen inside the piers.
The loggia was closed in, to a design by Simone di Francesco Talenti involving elegant mullioned windows in the late gothic style, and stained glass by Niccolò di Pietro Gerini showing Scenes and miracles of the Virgin (1395-1405).
Orsanmichele was completed in 1404. The tabernacles around the outside were assigned to the ‘Arti Maggiori’ or principal guilds (the Cloth-Merchants or Calimala, the Judges and Notaries, the Bankers, the Woolworkers, the Furriers, the Physicians and Apothecaries, the Silkworkers), to the ‘Mediane’ or medium guilds (the Butchers, the Cobblers, the Stonemasons and Woodworkers, the Blacksmiths, the Linenworkers and Ragmen), and to the guild of the Armourers and Swordmakers. The most important tabernacle, in the centre of the façade facing Via de’ Calzaioli, was assigned first to the Parte Guelfa and then to the Tribunal of the Mercatanzia.
All these institutions commissioned sculptures of their patron saints for their tabernacles, from the foremost Florentine artists of the 15th (Nanni di Banco, Ghiberti, Donatello) and 16th century (Giambologna).
The patron saints of the individual guilds, massed together on the four sides of the building, thus became the patron saints of the church of Orsanmichele itself.

The statues are currently being restored one by one and moved to the upper floor of the former granary, now the Museum of Orsanmichele (reached by the bridge from the adjacent Palazzo dell’Arte della Lana), their places in the niches being filled by copies. However, Donatello’s St George (1417) from the Armourers’ and Swordmakers’ tabernacle was moved to the Bargello in 1892 and replaced by a bronze copy Today replaced again with a copy in marble, while his St Louis of Toulouse (1433) is now in the Museum of Santa Croce. When its tabernacle passed to the Tribunal of the Mercantanzia, the St Louis was replaced by Verrocchio’s masterpiece, the group of the Incredulity of St Thomas (1467-83). Those guilds which did not have the priveledge of an external tabernacle had to make do with one inside the building, with their patron saint depicted in fresco or on panel.

The interior of Orsanmichele preserves its late gothic appearance almost intact: its square layout and the positioning of the piers recall the arrangement of the original open loggia. This explains the unusual position of the Madonna delle Grazie altar, not in the centre but to the right. To the left of the nave is the votive altar of St Anne, built by order of the Signoria in 1379, with a marble group of St Anne, the Virgin and Child by Francesco da Sangallo (c. 1526).

The museum has yet to be completed. The statues that are still located on the outside of the building are still waiting to be restored and replaced with copies, like the others already displayed inside the museum.