Saint Fillan, Filan, Phillan, Fáelán (Old Irish) or Faolán (modern Gaeilge & Gàidhlig) is the name of an eighth century monk from Munster, who having studied at Taghmon Abbey, traveled to Scotland and settled at Strath Fillan.

The name Fillan probably means "little wolf" in Irish / Gaeilge, being formed on a diminutive of faol, an old word for the animal. In Irish/Gaeilge the name Faolán is pronounced 'Fway-lawn'.

St. Fillan of Munster, the son of Feriach, grandson of Cellach Cualann, King of Leinster, received the monastic habit at the Abbey of Fintán of Taghmon in Wexford and came to Scotland from Ireland in 717 as a hermit along with his Irish princess-mother St. Kentigerna, and his Irish prince-uncle St. Comgan. They settled at Loch Duich.

After spending some time with his uncle Saint Comgan at Lochalsh, where Killilan (Kilfillan) bears his name, the saint devoted himself to the evangelization of the district of Perthshire round Strath Fillan, which is called after him, and where he was greatly venerated. St. Fillan was the abbot of a monastery in Fife before retiring to Glen Dochart and Strathfillan near Tyndrum in Perthshire.

A story is told that while St. Fillan was ploughing the fields near Killin, a wolf took the life of the ox and thus Fillan could not continue. A geis was put on the ox, which meant the wolf had to take the place of the ox and do its work. The story may be considered more of a parable than historical truth, but the connection with the origins of Fillan's name remains obvious.

St. Fillan was credited with powers such as the healing of the sick and also possessed a luminous glow from his left arm which he used to study and copy Sacred Scripture in the dark.

At an Augustinian priory at Kirkton Farm along to the West Highland Way, the priory's lay abbot, who was its superior in the reign of William the Lion, held high rank in the Scottish kingdom. This monastery was restored in the reign of Robert I of Scotland (Robert the Bruce), and became a cell of the abbey of canons regular at Inchaffray Abbey. The new foundation received a grant from King Robert, in gratitude for the aid which he was supposed to have obtained from a relic of the saint (an arm-bone) on the eve of the great victory over King Edward II's army at the Battle of Bannockburn. The saint's original chapel was up river, slightly northwest of the abbey and adjacent to a deep body of water which became known as St. Fillan's Pool.

The Mayne was an arm bone, now lost, enclosed in a silver reliquary or casket. The success of the Scots at Bannockburn was attributed to the presence of the arm of Saint Fillan, which was borne by its custodian, the Abbot of Inchaffray, on the field of battle. Legend has it that King Robert the Bruce requested the bone be brought to the Bannockburn battle site. The deoir, hereditary keeper of the relic, and the Abbot of Inchaffray Abbey left the bone behind and brought only the reliquary because they didn't want the relic to fall into English possession. On the eve of the Bannockburn battle, as the deoir, the abbot and Robert knelt in prayer, a noise came from the reliquary. They looked at the reliquary as the door opened and the bone fell to the floor. The Bruce won the battle the next day and established a monastery to thank St. Fillan for the victory.