A klobuk is an item of clerical clothing worn by Eastern Orthodox and Eastern Catholic monastics and bishops, especially in the Russian tradition. It is composed of a kamilavka (stiffened black headcovering, round and flat on the top) with an epanokamelavkion which completely covers the kamilavka and hangs down over the shoulders and back.
The klobuk is the headgear most often worn in church by professed monastics. During the services, there are specified times when monks are to remove the klobuk and lay it on their left shoulder to denote reverence for the sacred (for instance, when the Priest brings the Chalice out through the Holy Doors for the distribution of Holy Communion during the Divine Liturgy). Nuns do not normally remove the klobuk at any time during services.
The klobuk is often worn by bishops also. Diocesan bishops wear the simple monastic klobuk. Slavic Archbishops and Metropolitans usually wear a small jewelled cross on the front of their klobuk as a mark of their rank . Metropolitans wear a klobuk that is white rather than black .
The Patriarch of Romania wears a white klobuk as well as a white Ryassa. The Patriarchs of some Orthodox Churches (for example, the Patriarch of Moscow) wear a white headress similar to the klobuk that is rounded on top, decorated with embroidered images of seraphim, and surmounted with a cross .
Patriarchs and bishops of the Coptic Catholic  and Armenian Catholic  churches wear klobuks as well, although it is not a headgear worn by their Oriental Orthodox counterparts. Red klobuks have been worn by a Coptic Catholic patriarch , an Armenian Catholic catholicos , and a Ukrainian Catholic major archbishop  after being elevated to the cardinalate. A purple klobuk has been used by a Ukrainian Catholic bishop .