A catholicosate or catholicate is a particular ecclesiastical primacy, headed by a primate titled as a catholicos.
Such regional primacies exist within various branches of Eastern Christianity, especially those of Oriental Orthodox tradition.
The term catholicosate also designates the area of responsibility (territorial or otherwise) of a catholicos.
The word is derived from the Greek Καθολικος, meaning "wholeness", and it was used to designate ecclesiastical primacy of some major metropolitan sees.
While a catholicos is sometimes considered to correspond to a bishop in the Roman Catholic and Protestant traditions, a catholicate is typically a larger and more significant organizational division than a bishopric, archdiocese or episcopal see.