San Cassiano is a 14th-century Roman Catholic church located in the San Polo sestiere of the Italian city of Venice. A church has stood on the site since 726 with the present building dedicated to Saint Cassian of Imola being consecrated in 1376 and re-modelled during the 17th century. It has a plain exterior with several adjacent buildings overlapping it. Its interior however is richly decorated in a Baroque style.
The church is located on the Campo San Cassiano, site of the world's first public opera house, west of the Rialto Bridge and is open to visitors Tuesday-Saturday mornings.The church houses three paintings by the Italian artist Tintoretto, including The Crucifixion of Christ painted in 1568 which the art critic John Ruskin described as, "the finest [example of a Crucifixion painting] in Europe".
However, the most famous painting associated with the church is paradoxically one which is no longer there. The San Cassiano altarpiece, painted for this church by Antonello da Messina, was the first major example of oil painting in the city. It disappeared from the church in the 17th century and was cut into sections; the remaining known pieces are re-united in Vienna.