Torsnes is a former municipality in Østfold county, Norway.
It was created by a split from Borge on 1 January 1910. At that time Torsnes had a population of 1,538.
On 1 January 1964 the properties Gansrød and Ulfeng, with 30 inhabitants, were incorporated into Fredrikstad while the rest of Torsnes, with 1,274 inhabitants, was reunited with Borge. On 1 January 1994, Borge was incorporated into Fredrikstad.
The Norse form of the name was Þórsnes. The first element is the genitive case of the name of the god Þórr, the last element is nes n 'headland; peninsula'. (The neighbouring island has the name Ullerøy, from the name of the god Ullr.)
An old farm in the parish, close to the church site, has the name Tose (from Norse Þórshof). This is a compound of Þórr and hof, Norse meaning "Thor's temple."