The patron saint of Sant'Olcese is Saint John the Baptist, celebrated on 24 June, with the 17th-century oratory dedicated to him in the hamlet of the same name. The town itself, however, takes its name from bishop Olcese who, according to tradition, fled to this area in the 5th century because of the barbarian invasions of Gaul: the territory's ancient place name in Roman times was Valle Ombrosa, later changed in the bishop's honour. His relics, found in 1155, are now kept in a gilded wooden urn in the parish church dedicated to him, first mentioned in a document from 1143 and perhaps founded by Columbanian monks, rebuilt with three naves in 1387 and solemnly consecrated in 1635: on its façade a painting depicts the «miracle of the bear», according to which the saint tamed a bear that was terrorising the town, yoking it to a cart in place of an ox killed by the beast.
The territory of Sant'Olcese followed the historical events of Borzoli, today a district of Genoa, becoming part of the properties of the marquises of Savona and, from 1216, of those of the bishop of Albenga Oberto II. Sant'Olcese is also known today for its typical coarse-ground salami, included in the list of traditional Italian agri-food products, and for Forte Diamante, the rearmost of the defensive structures surrounding Genoa, built in the second half of the 18th century.
