The Roman name of this small vicus was Indiciacum or Indiciacus, which evolved into Indiciat in the sub-Roman period, a reference to the landmark of Planèze.

Early, perhaps as early as the fifth century,[4] Florus of Lodève, credited in medieval tradition with being the first bishop of Lodève and belonging to the apostolic era,[5] arrived to Christianize the valley, and gave his name to the area, striking a rock with his staff, it was said, to create a holy spring that continued to be venerated under its Christianized guise, into the 20th century.

[6] The present town called Indiciac took shape only around the millennium, clustered around the monastery founded on the high rock in 996, at first little more than an oratory.

The site, already occupied by a small monastic community, was donated to Odilo of Cluny by the Auvergnat seigneur, Astorg de Brezons;[7] the donation was confirmed by Pope Gregory V, i.e. in 996–99, but Astorg's nephew, Amblard "le mal Hiverné" ("the furious"), the comptour[8] perhaps asserting residual family interests in the place, seized it and laid it waste, sparing the church.

The troubadour Bernart Amoros recalled to his readers that he came from Saint-Flour:Eu Bernartz Amoros clerges scriptors daquest libre si fui d'Alvergna don son estat maint bon trobador, e fui d'una villa que a nom Saint Flor de Planeza[13]Poet Pierre-Laurent Buirette de Belloy (1727–95), author of a once-celebrated tragedy on the Siege of Calais, was born at Saint-Flour.