Greetings.
Yes, there is a St. Judas but (as you may naturally suspect) he is not Judas Iscariot. The name “Judas” is the Greek variation of the Hebrew name “Judah”, and two of the apostles had this name: Judas, identified as “the son of James” (see Luke 6:16 and Acts 1:13), and Judas Iscariot (the betrayer of Jesus). In Matthew 10:3 and Mark 3:18, this former Judas is given the name of “Thaddeus” (or “Thaddaeus”, depending on your Bible translation). One of the epistles of the New Testament is attributed to him.
To avoid confusion, Christians have customarily taken measures to make proper distinctions between these two apostles. For example, in his gospel, St. John mentions, “Judas (not Iscariot)” (John 14:22). Many people combine the two New Testament names for the saintly Judas, resulting in, “Judas Thaddeus” (considering Thaddeus to be a surname). These days the most common method is to simply shorten his name from “Judas” to “Jude.”
If you came across a reference simply to “St. Judas”, I suppose the presumption is that the reader would be aware that there were two men named Judas among the apostles, and therefore this is the saintly Judas (the son of James) and not Judas Iscariot (who is most definitely
not considered a saint by the Church).
When looking for information concerning Judas Thaddeus, it is probably best to simply use the name of “St. Jude”. Here are some links for more information concerning him:
St. Jude – Apostle
Novena to St. Jude
Litany to St. Jude