The Epistle to the Easterns is an apostolic letter sent by Pope Pius IX in 1848 to the bishops and clergy of the Orthodox Churches not in full Communion with the Pope, urging them to resume such Communion.
The Epistle is the first of a series of apostolic letters and encyclicals published by Pius IX defining the terms and conditions for a reunification between the Roman Church and the Orthodox Churches, after the Great Schism of 1054. The Pope's attitudes were later confirmed by the First Vatican Council, over which he presided.
The letter was answered the same year by several leading members of the Orthodox Church, in the Encyclical of the Eastern Patriarchs, which restated the theological controversies between the two Churches, most notably the dispute over the addition of the filioque to the Nicene Creed, and papal supremacy.