Church of the Assumption of the Virgin Mary, Gothic church in Mladá Boleslav I, Czech Republic.

The Church of the Assumption of the Virgin Mary is a late Gothic hall church with three aisles and a wide polygonal presbytery, founded after 1406 and vaulted in 1566. Its Baroque facade with a panel gable and the two-storey porch by M. Rossi (1701–1702) close the Old Town Square. A Gothic tin font from 1489 survives inside.

Founded after 1406, the church was walled up by the mid-15th century and burned in 1538; it was repaired and vaulted in 1566. Until the period after the Battle of White Mountain it was the main church of the Czech Utraquist church, and in 1623 it was adapted for the Roman Catholic rite, when the chalice in the gable was destroyed. It was partly baroqued in 1665, baroqued again in 1701–1702 and 1761, and restored in 1906–1908.

A chalice appears in the tracery of one window of the main façade and another in the keystone of the portal to 9. května street, reminders of the church's Reformation past as the main church of the Czech Utraquists. In 1623 the chalice in the gable was destroyed when the church was adapted for the Roman Catholic rite.

The building is open to visitors as a cultural monument and offers insight into its architectural and artistic features. It continues to serve for regular religious ceremonies, so it is helpful to check in advance when such gatherings take place.

The Gothic tin baptismal font survives from 1489 and carries figures of saints; the church pews date to around 1730. A chalice appears in the tracery of one window of the main façade and in the keystone of the portal to 9. května street, recalling the Hussite period.