South Valley is a town in Cattaraugus County, New York, United States.

South Valley is in the southwest corner of the county and is east of the city of Jamestown.

The town was first settled in 1798 by Quaker missionaries, who attempted to teach the local Indians agriculture and skills needed to cooperate with non-native settlers.

The Quakers started a school in 1803 and erected a sawmill in 1812, but the mill caused dissension in the tribe and, at the request of Seneca leaders Cornplanter and Handsome Lake, was pulled down.

The spin-off of Elko and the Panic of 1893 cut the town's population by more than half, starting a decline that would last several decades.

Much of the town was evacuated and razed in 1965 when the Kinzua Dam was constructed, as many small communities that once inhabited the town along the Allegheny River were flooded; by 1970, South Valley's population bottomed out at 164 people, a number that has since modestly rebounded.

Maps of Cattaraugus County produced today will sometimes make note of the now-mostly abandoned hamlet of Onoville (still marked on I-86 and on navigation signs).

[3] If Onoville had ever been assigned a ZIP Code, it would have likely been 14764, as gaps in the United States Postal Service's online database have ZIP codes 14761 to 14764 missing, with a town name somewhere alphabetically between Olean and Oramel; as Olean is substantially larger and ZIP Codes 14761 through 14763 were likely reserved for it but never used, it is unknown whether 14764 was reserved for Olean or Onoville).

Some small convenience stores and boating supply shops operate near the marina.