Saint Cathan, also known as Catan, Cattan, etc., was a 6th-century Irish monk revered as a saint in parts of the Scottish Hebrides.

This Saint appears in the Aberdeen Breviary, Walter Bower's Scotichronicon, and the Acta Sanctorum, and a number of placenames in western Scotland are associated with him.^[1][2]

He is said to have been one of the first Irish missionaries to come to the Isle of Bute, then part of the Gaelic Kingdom of Dál Riata.

Very little is known of him; he is generally only mentioned in connection with his more famous nephew Saint Blane, who was born on Bute and later proselytized among the Picts. Both saints were strongly associated with Bute and with Kingarth monastery, which became the center of their cults.^[3][4]

A number of churches were dedicated to Cathan across Scotland's western islands.

• Tobar Chattan, or Cathan's Well, at Little Kilchattan on Bute may represent the site of Cathan's original church.^[3]
• Other churches, now in ruins, include St Cathan's Chapel on Colonsay,
• Kilchattan Chapel on Gigha, and
• Kilchattan Church on Luing.^[5][6][7] The Luing church served the historical Kilchattan parish; the modern Kilchattan Church was built at Achafolla in 1936.^[8]

Cathan is said to have lived for a time at the monastery at Stornoway on the isle of Lewis, and his relics are said to have been housed at a chapel founded by Clan MacLeod on the same island.^[9]