Sant'Ambrogio Chuch, Gothic Catholic church in Santa Croce district, Florence, Italy

Sant'Ambrogio is a Gothic church in the Santa Croce district of Florence featuring pointed arches on its exterior facade and a decorated high altar inside. The interior combines architectural elements from different construction phases with religious artworks distributed across walls and side chapels.

First recorded in 988 (possibly older), the church was rebuilt in Gothic forms at the end of the 13th century, when it was enlarged for the devotion stirred by the 1230 Eucharistic miracle. Giovanni Battista Foggini rebuilt it in the 17th century. The Chapel of the Miracle received Mino da Fiesole's marble tabernacle (1481–1483) and Cosimo Rosselli's fresco of the Miracle of the Chalice around 1486.

The name comes from Saint Ambrose, said to have stayed here in 393; a polychrome terracotta tabernacle by Giovanni Della Robbia on the square shows the bishop blessing passers-by. The Compagnia del Corpus Christi was founded here after the 1230 miracle, and the Cappella del miracolo, frescoed by Cosimo Rosselli around 1486, depicts a 1340 procession that was believed to have saved Florence from the plague.

The church stands on Piazza Sant'Ambrogio in the eastern part of Florence's historic centre, north of Santa Croce, on the side of the city that lay outside Arnolfo di Cambio's walls of 1284–1310. The square is marked by a polychrome terracotta tabernacle by Giovanni Della Robbia showing Saint Ambrose blessing passers-by. The facade is plain and undecorated, so the entrance is easy to miss.

The relic is the ampoule of blood from the 1230 Eucharistic miracle: the priest Uguccione found clotted blood in a chalice he had left unwashed. Bishop Ardingus kept the ampoule for a year to verify it, and Mino da Fiesole's marble tabernacle (1481–1483) shows Uguccione entrusting it to the abbess. Mino asked to be buried before his own work.