This Advent hymn dates back at least to the 7th Century. At one time it was attributed to St. Ambrose, but his authorship is no longer considered likely. It has long been sung during Advent, especially at Vespers services..
Here is the hymn chanted by the Cistercian Monks of Stift Heiligenkreuz, a monastery in the southern part of the Vienna woods:
This chant has served as the basis for motets written by many composers, including Guillaume Dufay, Orlande de Lassus, Francisco Guerrero, Giovanni Luigi da Palestrina, Tomás Luis de Victoria, Ludwig Senfl, Michael Praetorius, and Jean Titelouze.
Below is the Latin text and a fairly literal English translation. The translation in our Hymnal takes some liberties with the Latin to respect the demands of meter and rhyme in English poetry. (See this post for a discussion of a few medieval translations of this Latin poem.)
1 Conditor alme siderum
Kind creator of the stars,
aetérna lux credéntium
eternal light of those who believe,
Christe redémptor ómnium
O Christ, Redeemer of all,
exáudi preces súpplicum
hear the petitions of your suppliants.
2 Qui cóndolens intéritu
You are the one, having compassion
mortis perire saeculum
that the race should perish in the destruction of death,
salvásti mundum languidum
who saved the fainting world,
donans reis remedium.
giving the remedy to all things.
3 Vergénte mundi véspere
When the world’s evening drew to an end,
uti sponsus de thálamo
as the spouse from his chamber,
he came forth from the most honored
Virginis matris cláusula.
womb of a Virgin Mother.
4 Cuius forti ponténtiae
To whose almighty power all are bowed
genu curvántur ómnia
on bended knee,
things of heaven and earth,
nutu faténtur súbdita.
acknowledging themselves submitted to his command.
5 Te, Sancte fide quáesumus,
O you, Holy One, we ask in faith,
venture judex sáeculi,
O coming judge of the world,
consérva nos in témpore
preserve us in our time
hostis a telo perfidi.
from the dart of the treacherous foe.
6 Sit, Christe rex piissime
To you, O Christ, king most loving,
tibi Patríque glória
and to the Father be glory
cum Spíritu Paráclito
with the Spirit, the Paraclete,
in sempitérna sáecula. Amen.
for everlasting ages. Amen.