I use an admittedly idiosyncratic term to describe a set of Christian Saints who were involved in establishing, profoundly shaping, or reforming the various liturgies of the Church; I call them the Liturgical Fathers. These are Saints who are known to have an important influence on the public worship of the Church through the spoken prayers, symbolic gestures, and chanted song used in the Divine Liturgy.
I tend to think of St. James the Just (Brother of God), St. Mark the Evangelist, St. John Chrysostom (meaning Golden-tongued), St. Basil the Great, St. Gregory the Great, and St. Ambrose of Milan as being collectively the Liturgical Fathers. James the Just, Mark the Evangelist, and John Chrysostom all have liturgies named after them because of their great influence on the liturgical forms of their respective patriarchates.
Basil the Great and Gregory the Great are both known to be effective reformers of the liturgies which existed at the time of their work in the Church. Gregorian chant (named for Pope Gregory the Great) and Ambrosian chant (named for St. Ambrose of Milan) are known in the West especially as beautiful forms of sacred music well-suited to the praise and worship of God the Father, Son, and Holy Spirit.
While the Divine Liturgy of St. James, the Divine Liturgy of St. Mark, the Divine Liturgy of St. John Chrysostom, the Divine Liturgy of St. Basil the Great, the Latin Rite reformed by St. Gregory the Great, and the Ambrosian Rite named after St. Ambrose of Milan are not the only liturgies of the Church, I've chosen not to include some others in the group of Liturgical Fathers.
St. Tikhon of Moscow, for example, was a liturgical reformer who has a liturgy named after him. I've not included him in the list of Liturgical Fathers primarily because, like Pope Paul VI, he's a modern reformer of the liturgy. That's not necessarily a bad thing. I have no particular objections to the reforms of either Patriarch, and I generally think they made the right decision with regard to allowing the use of English in the liturgy, for example.
As for the African Rite, Celtic Rite, the Gallican Rite, and the Mozarabic Rite, I'm not aware of a clear case of a Saint causing them to exist or be reformed. Nor are they currently practiced in the West except for a few very minor exceptions. Those liturgical Rites seem to be more a subject of study now than a lived expression of the ancient Christian faith, for better or worse.
In the end, I tend to think of the Liturgical Fathers as the founders and reformers of liturgies and musical traditions which are still currently in use. I'm not sure how much longer St. Ambrose's music will be used, but I can attest that it's still used now. I'm going to be singing some of it soon at my parish, after all.
Gregorian chant is still going strong, and if anything seems more popular than ever even in secular culture. I've attended the Divine Liturgies of St. Basil the Great and St. John Chrysostom in this past year, and while I haven't yet attended the Divine Liturgy of St. James or the Divine Liturgy of St. Mark, I do know people who have attended them relatively recently.
It's a real testament to the strength of Christian tradition that these liturgies are still around, and that surprisingly little has changed about them. I'm grateful to the Liturgical Fathers for the treasures they preserved and reformed.
We have a profound responsibility to be good stewards of the ancient liturgies (just as the Liturgical Fathers were) so that the Christians who come after us can experience their spiritual riches as well.
St. James the Just, ora pro nobis.
St. Mark the Evangelist, ora pro nobis.
St. John Chrysostom, ora pro nobis.
St. Basil the Great, ora pro nobis.
St. Gregory the Great, ora pro nobis.
St. Ambrose of Milan, ora pro nobis.
Related: What is liturgy and why does it matter?
Note: The above images of icons are all icons I've purchased from orthodoxmonasteryicons.com or bostonmonks.com, and I recommend their icons for those who want positive and spiritually beneficial Christian art to aid their prayer life.