Settlements of the 19th-century Neolithic and Bronze Age were discovered near and in Lake Zürich. In 2004, a formerly unknown Celtic, Iron Age La Tene settlement was discovered on the previous site of the Otenbach monastery in the city, which preceded the Romans.

In Roman times, a provincial civilian settlement, called Turicum, was situated on the territory of present-day Zürich, which was initially the Roman province of Gallia Belgica and Upper Germania after AD 90. Upper Germania comprised southwest Germany, the French Alsace and Jura regions, as well as western Switzerland.

After Emperor Constantine’s reforms in AD 318, the border between Gaul and Italy (two of the four praetorian prefectures of the Roman Empire) was located east of Turicum, crossing the Linth River between Lake Walen and Lake Zürich, where a castle and garrison looked over Turicum’s safety. The earliest written record of the town dates from the 2nd century, with a tombstone referring to this castle discovered at Lindenhof, in Zürich.

The patron saints of Zürich are Felix and Regula and their feast day is September 11. Legend has it that they were siblings in the Theban legion. The legion members were to be executed in AD 286, thus the siblings fled to Zürich, where they were caught, tried and executed. They continued walking uphill after they had been decapitated and were buried on the spot where they finally collapsed. A small abbey stood on this site in the 9th century. Around 1100, the Great Minster, one of Zürich's three most impressive churches, was built on their graves, and the Wasser Church was erected on the site of their execution. Images of the saints began to be used on coins and official city seals in the 1200s.
 
In the 5th century, the Germanic Alamanni tribe settled in the Swiss plateau, which comprises the regions between the Alps and Jura and forms some 30 percent of modern-day Swiss territory. The Roman castle remained standing until the 7th century. The earliest historic mention of the Germanic settlement describes the mission of St Columbanus in AD 610. Canonised after his death, this Irish missionary founded numerous monasteries in the Italian and Frankish kingdoms around AD 590. 

Ziurichi is mentioned on an 8th-century toponymic list from Ravenna, a city in the Italian region of Emilia-Romagna. Here is a mythical account of the Germanic duke Uotila living on, and giving his name to, the Uetliberg mountain, which is located in the Swiss plateau, which offers a memorable view of Zürich and its lake.