In AD 746, Zürich became part of Alemannia, after Frankish Duke Carloman executed several thousand noblemen for treason at a council in Cannstatt, known as the 'blood court at Cannstatt'. The independence of the duchy of Alemannia came to an end, and was ruled by Frankish dukes thereafter.
 
The ruined Roman castle was replaced by a castle of the Carolingian dynasty, built by Louis the German, the grandson of Charlemagne, whose representatives eventually became the kings of the Franks. Louis also built the Benedictine convent Fraumunster abbey, and gave it authority over Albis forest and the lands of Uri and Zürich. By placing the convent under his direct authority, he granted it immunity. In 1045, Henry III gave the convent permission to hold markets, mint coins and collect tolls. The abbess was the effective ruler of the city as a result.

In 1218, Zürich attained a status comparable to statehood, after the last of the Zahringers, a German noble family, died. During the 1230s, a city wall enclosing 38 hectares was built, when the earliest stone houses at the Rennweg were built as well. The Carolingian castle was used as a quarry, as it had started to fall into ruin.

In 1234, Emperor Frederick II promoted the abbess of the Fraumunsterrank to duchess, who in turn appointed the mayor from then on. The duchess often delegated the minting of coins to citizens of the city. However, the political influence of the convent began to diminish in the 1300s, a process motivated by the establishment of guild laws by Rudolf Brun in 1336. Brun became the first mayor not appointed by the abbess. The guilds came to dominate the city, and as a consequence of the Protestant reformation in the 16th Century, the monasteries diminished. However, an important event in the early 14th Century was the completion of the Manesse Codex, a key source of medieval German poetry written and illustrated in Zürich.