A litany is a ceremonial or liturgical form of prayer consisting of a series of invocations or supplications with responses that are the same for a number in succession.
Just like novenas, there are many different litanies to many different saints or for many different petitions. Here below is the litany to our patroness. You can search for other litanies using the link on the right side of the page.
Lord, have mercy on us. Christ, have mercy on us.
Lord, have mercy on us. Christ hear us. Christ, graciously hear us.
God the Father of heaven, Have mercy on us.
God the Son, Redeemer of the world, Have mercy on us.
God the Holy Spirit, Have mercy on us.
Holy Trinity, one God, Have mercy on us.
Holy Mary, Pray for us. (repeat after each line)
St. Dominic, glorious Patriarch,
St. Catherine of Siena,
Benevolent mother of the poor,
Merciful mother of the sick,
Refuge of the sorrowful,
Intercessor for sinners,
Rose of patience,
Model of humility,
Lily of chastity,
Vessel of graces,
Zealous promoter of the honor of God,
Luster of holiness,
Example of mildness,
Glory of the Order of Preachers,
Fruitful mother of spiritual children,
Promoter of peace,
Terror of the evil spirits,
Follower of Jesus,
St. Catherine, who did give the blossoms of your innocent youth to the service of your Heavenly Spouse,
St. Catherine, whom Jesus Himself did feed with His Body and Blood,
St. Catherine, who exchanged her heart with the Heart of Jesus,
St. Catherine, who was blest with His Holy Wounds,
St. Catherine, who was taken to Heaven to the celestial nuptials,
St. Catherine, who did receive a hundredfold, reward for all her labors and merits,
Lamb of God, you take away the sins of the world, Spare us, O Lord.
Lamb of God, you take away the sins of the world, Graciously hear us, O Lord.
Lamb of God, you take away the sins of the world, Have mercy on us.
Pray for us, O glorious Virgin, St. Catherine, That we may be made worthy of the promises of Christ.
Let us pray, O God, who gave St. Catherine, graced with the special privilege of virginity, patience to overcome the assault of evil spirits and to stand unshaken in the love of your Name. Grant we beseech you, that after her example treading under foot the wickedness of the world and overcoming the wiles of all enemies, we may safely pass onward to your glory. Through Christ our Lord. Amen.
Source: Kyrie Eleison — Two Hundred Litanies by Benjamin Francis Musser O.F.M., The Magnificat Press, 1944