Gloria in Excelsis Deo

At the bottom of this post, you can find a YouTube video recording of the Gregorian chant Gloria in Excelsis Deo, and this Wikipedia article provides a history of the use of this hymn in both the eastern and western churches.

Here are the Latin lyrics:

Gloria in excelsis Deo, 

et in terra pax hominibus bonae voluntatis. 

Laudamus te, benedicimus te, 
adoramus te, glorificamus te, 

gratias agimus tibi propter magnam gloriam tuam, 

Domine Deus, Rex caelestis, Deus Pater omnipotens. 

Domine fili unigenite, Jesu Christe, 

Domine Deus, Agnus Dei, Filius patris, 

Qui tollis peccata mundi, miserere nobis. 

Qui tollis peccata mundi, suscipe deprecationem nostram. 

Qui sedes ad dexteram Patris, miserere nobis. 

Quoniam tu solus sanctus, 

Tu solus Dominus, 

Tu solus Altissimus, Jesu Christe, 

Cum Sancto Spiritu in gloria Dei Patris. 
Amen.

(19th-century stained glass)