Theos Kyrios

Theos Kyrios (Greek: Θέος Κύριος, "God is the Lord", or "The Lord is God") is a psalm response chanted near the beginning of the Matins service in the Rite of Constantinople, observed by the Eastern Orthodox and Byzantine Catholic churches. It is based principally on Psalm 117 (Septuagint numbering), the refrain composed of verses v. 27a and 26a.

Theos Kyrios comes after the Great Ektenia (litany) and precedes the apolytikion (troparion of the day), and is chanted in the tone of the week. While the Typicon (book of rubrics) prescribes that the verses should be chanted by the canonarch standing in the center of the nave, in the Byzantine practice the verses are intoned by the psalmist (Cantor_(church)). In common Slavic practice they are chanted by the deacon standing before the icon of Christ on the iconostasis; if there is no deacon, the verses are commonly read by the priest.

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