Goar (Latin Goarius, Frankish Goharius — the etymology preserves an Old Frankish 'good-warrior' meaning) was — per the foundational Vita Sancti Goaris composed in the 9th century by Wandalbert of Prüm — born around 495 AD in Aquitaine to a Gallo-Roman Christian family. He was ordained priest in his Aquitanian native diocese and at about 50 years of age (around 545 AD) withdrew from his Aquitanian parish to become a hermit-priest on the Middle Rhine, at the dangerous narrow stretch of river immediately upstream of the famous Lorelei rock (where the Middle Rhine cuts through the Hunsrück mountains and produces one of the most treacherous river-navigation stretches in pre-modern Western Europe).
Goar established his hermit-cell on the eastern bank of the Rhine at the small location that has been called Sankt Goar ever since. The dangerous Rhine-navigation stretch immediately downstream meant that substantial numbers of Frankish-Rhenish river travellers were forced to pause at his hermit-cell location before attempting the Lorelei crossing. Goar — combining his eremitic prayer-life with substantial pastoral hospitality to the river travellers — established the foundational pattern of the Catholic Rhineland Christian hospitality-monastery that would become characteristic of the medieval Rhine-Mosel monastic system.
He died at his hermit-cell on July 6, 575. The small church and pilgrim-hospice he had established was substantially expanded across the medieval period into the Stiftskirche Sankt Goar (the small medieval collegiate church of Sankt Goar on the Middle Rhine), which became a foundational Rhineland-Catholic pilgrimage site. The town of Sankt Goar (named for him) is one of the foundational continuous Rhineland-Catholic civic identities.