In architecture, bacini (plural, singular Italian: bacino, IPA: [baˈtʃiːno], "bowl") are ceramic bowls that were used for decoration in the medieval Europe. The bowls were embedded into the external walls of (mostly religious) buildings and are thus also known as immured vessels. Bacini represent one of the traits of the Pisan Romanesque style. They can also be found in the Byzantine and Gothic buildings.

The Italian word "bacini" is used in many languages in the modern sense - to designate glazed vessels that were not specifically designed as architectural decorations, but were used for that purpose - since at least the 18th-19th centuries. The term does not define a particular type of the vessel that is immured: both bowls and plates had been used as bacini.

Regarding the bacini's origins, most scholars declare them to be a medieval - and European - invention. However, some researchers point to few immured cups found in the buildings of Ostia Antica and Islamic architecture that extensively used the glazed ceramics (but not bacini). Megaw thinks that the practice spread to Italy from the Byzantine Empire.

The bacini were most popular in Italy, but their use was widespread between late 10th and 15th centuries, primarily in the coastal regions of the Mediterranean. The bowls can be found in the buildings of Spain (Seville, Zaragoza, Calatayud, Teruel), Southern France, Sardinia, and Corsica. In Northern Italy bacini can be found both on the coast and inland, in Liguria, Veneto, Padua, Verona, Lombardy, Ticino (now in Switzerland), Piedmont, Emilia Romagna, Umbria, and Abruzzo. The largest concentration is in Tuscany (especially in the vicinity of Pisa) and Lazio. While common in Rome, very few examples can be found farther south in Campagna, Apulia, Calabria, and Sicily. To the east, bacini appear on the Dalmatian coast (Zadar, Trogir) and continue into the Byzantine territory, including areas of Greece.

In Italy, the number of buildings decorated with immured bowls in a single city varies: 4-10 in Milan, Ferrara, Ravenna, Genoa, Lucca, Sassari, Ascoli Piceno, 15 in Pavia and Bologna, more than 20 in Rome and Pisa.

After the 15th century, bacini were used only "sporadically".

The bowls were not ordered specifically for decorating the buildings, they were simply selected from regular (and expensive) dishware. There is no evidence of selecting particular drawings or even colors. For a long time the bacini were imported. While Italian pieces appeared in the 13th century (in Liguria), they only started to constitute the majority of the supply since the 14th century (and the importation never stopped). Imported pieces were coming from al-Andalus, Egypt, Maghreb, Balearic Islands, later - from Sicily, Southern Italy, Byzantine Empire. Part of the bacini's attraction apparently came from the exotic sourcing: there were very few cases of bacini used for decoration in places where they were manufactured (like Sicily).

Bacini were used in quantity, buildings with just one or two installed are rare. Some churches in Pisa (San Piero a Grado, San Martino, Santa Cecilia [it]) had over 200 bacini each. The location of bacini in the building varied, but typically they were placed high up: at the clerestory level, in the blind arcades, on the sides of bell towers. Occasionally, the bowls on the facades were arranged into a figure of cross. Five-bacini crosses were popular in Crete, and are quie rare in mainland Greece and Italy. The places for the bacini were designed into the buildings: stones or bricks were cut or shifted to create the space for ceramics; once the piece was placed, the subsequent layers of masonry frequently blocked it in place, thus convincing the future researchers in the contemporaneity of the building and the bowls immured in its walls.