The Ex Chiesa di San Mattia is a deconsecrated church in Bologna attributed to Pietro Fiorini.

Annexed to the Convent of the Dominicans , with the simple façade overlooking Via Sant'Isaia, perfectly integrated into the urban fabric thanks to the portico placed in continuity with that of the neighboring buildings. The sumptuous and spectacular appearance of the interior is due to a modernization of the ornamental and pictorial apparatus carried out in the mid-eighteenth century by the quadraturist Pietro Scandellari and the artists Nicola Bertuzzi and Tertulliano Taroni. The transformation of the sixteenth-century serlianas and oculi in the central elevation into rectangular windows dates back to the same period. In 1799, following the suppression of religious orders by the Napoleonic government, the church of San Mattia was isolated from the convent, deconsecrated and reduced to a warehouse.

The restoration, begun in 1981 and completed in 1994, at the expense of the Ministry for Cultural Heritage and Activities, has brought to light what remained of the stuccoes and frescoes . Entrusted to the Regional Directorate for Cultural and Landscape Heritage of Emilia Romagna by the State Property Agency, the Ex Chiesa di San Mattia has become a venue for exhibitions, meetings, conferences dedicated to architecture, urban planning, design, study of the historical-artistic-landscape heritage of the Emilia-Romagna region.