Northwich is a market town and civil parish in the Cheshire West and Chester borough of Cheshire, England. It lies on the Cheshire Plain, at the confluence of the rivers Weaver and Dane, 18 miles (29 km) east of Chester, 15 miles (24 km) south of Warrington, 19 miles (31 km) south of Manchester, 69 miles (111 km) north of Birmingham, and 36 miles (58 km) south of Liverpool. The population of the parish was 22,726 at the 2021 census.

The area around Northwich was exploited for its salt pans by the Romans, when the settlement was known as Condate. The town had been severely affected by salt mining and subsidence was historically a significant problem. Mine stabilisation work was completed in 2007.

During Roman times, Northwich was known as Condate, thought to be a Latinisation of a Brittonic name meaning "Confluence". There are several other sites of the same name, mostly in France; in Northwich's case, it lies at the junction of the rivers Dane and Weaver.

Northwich can be identified through two contemporary Roman documents. The first of these is the Antonine Itinerary, a 3rd-century road map split into 14 sections. Two of these sections, or Itinerary, mention Condate: Route II ("the route from the Wall to the port of Rutupiae") and Route X ("the route from Glannoventa to Mediolanum"). The second document is the 7th-century Ravenna Cosmography; it refers to Condate between the entries for Salinae (now Middlewich, Cheshire) and Ratae (now Leicester, Leicestershire), at the time the capital of the Corieltauvi tribe.

The Romans' interest in the Northwich area is thought to be due to the strategic river crossing and the location of the salt brines. Salt was very important in Roman society; the Roman word salarium, linked employment, salt and soldiers, but the exact link is unclear. It is also theorised that this is the basis for the modern word salary. Another theory is that the word soldier itself comes from the Latin sal dare (to give salt). There is archaeological evidence of a Roman auxiliary fort within the area of Northwich, now known as "Castle", dated to AD 70. This, and other north-western forts, were built as the Romans moved north from their stronghold in Chester.

The association with salt continues in the etymology of Northwich. The "wich" (or "wych") suffix applies to other towns in the area: Middlewich, Nantwich and Leftwich. This is considered to have been derived from the Norse, wic for bay, and is associated with the more traditional method of obtaining salt by evaporating sea water. Therefore, a place for making salt became a wych-house; Northwich was the most northern of the -wich towns in Cheshire.

The existence of Northwich in the early medieval period is shown by its record in the Domesday Book of 1086:

In the same Mildestuic hundred, there was a third wich called Norwich [Northwich] and it was at farm for £8.