The Trisagion

Holy God,
Holy Mighty,
Holy Immortal,
have mercy on us.

Source: The Divine Liturgy of St. John Chrysostom

Source of this version: Modified from http://www.ocf.org/OrthodoxPage/liturgy/liturgy.html

The word Trisagion is Greek for “three-holy.” The prayer expands the “Holy, holy, holy” of Isaiah 6:13 and Revelation 4:8.

In original Greek:

Ἅγιος ὁ Θεός, Ἅγιος ἰσχυρός, Ἅγιος ἀθάνατος, ἐλέησον ἡμᾶς.

Hagios ho Theos, Hagios ischyros, Hagios athanatos, eleison imas.