Holy Mandylion church, Orthodox church in Staroselenginsk, Russia.

The Holy Mandylion church is a ruined five-domed Orthodox cathedral on the right bank of the Selenga near Novoselenginsk. Built of brick in 1784–1789, it measures 25.6 by 49.6 metres and stood about 40 metres high. Its crosses were removed from 1936, monks' cells were blown up in the 1950s, and part of the domes was demolished; the shell was later used as a cattle stall.

A wooden three-altar church of the Saviour, 32 metres high, was built in 1665 when the Selenginsk fortress was founded; it burned down on 4 April 1780. The stone cathedral was begun on 14 May 1784 with support from Empress Catherine II and donations, and finished on 13 June 1789. The architect was Vorotnikov, a self-taught townsman from Tyumen; the contractors were Ivan Basov and Dmitry Pakholkov. A slab from the grave of the exiled hetman Demyan Mnogogreshny was laid in the lower church floor.

The name refers to the Holy Mandylion, the image of Christ not made by hands, to which the main upper altar was consecrated; the lower church held a side altar to the Great Martyr Catherine in gratitude to Empress Catherine II. The exiled hetman Demyan Mnogogreshny's grave slab was laid in the lower church floor during construction. Since the 1930s the building has not served worship.

The cathedral stands in ruins on the right bank of the Selenga near Novoselenginsk, beside the surviving Chapel of the Holy Cross; these two are all that remain of Old Selenginsk. The building was stripped of its crosses from 1936 and later used as a cattle stall, so there are no services and no opening hours. Approach on the roads to Novoselenginsk and view the walls from outside.

In the floor of the lower church a slab from the grave of the exiled hetman Demyan Mnogogreshny was laid during construction. The self-taught architect was Vorotnikov, a Tyumen townsman, and the contractors were the future Selenginsk merchant Ivan Basov and the merchant Dmitry Pakholkov.