What title was held by the leader of the Eastern Orthodox Church?

The leader of the Eastern Orthodox Church is referred to as a Patriarch. This title denotes a high ecclesiastical office, and the Patriarch is regarded as the senior bishop of the Orthodox Christian community in a specific region. The Patriarch holds significant authority and is responsible for overseeing the spiritual and administrative functions of the church within their jurisdiction.

In the context of the Eastern Orthodox Church, the Patriarch of Constantinople is one of the most prominent figures. This role differs from that of the Pope in the Roman Catholic Church, who serves as the supreme leader of all Catholics worldwide. The title of Bishop applies to individual church leaders within the Orthodox Church, while Cardinal is a title specifically associated with the Catholic Church's hierarchy and is not found in the Eastern Orthodox tradition. Thus, the term Patriarch is the correct designation for the leader within the Eastern Orthodox framework.