Klein-Winternheim is an Ortsgemeinde – a municipality belonging to a Verbandsgemeinde, a kind of collective municipality – in the Mainz-Bingen district in Rhineland-Palatinate, Germany.

Klein-Winternheim lies seven kilometres south of Mainz in Rhenish Hesse. The winegrowing centre belongs to the Verbandsgemeinde of Nieder-Olm, whose seat is in the like-named town.

In the oldest Mainz Cathedral obituary from about 1100, the name Winterheim crops up for the first time.

The council is made up of 20 council members, plus the part-time mayor, with seats apportioned thus:

	CDU	SPD	FWG	Total
2024	8	4	8	20 seats

(as at municipal election held on 9 June 2024)

• Muizon, Marne, France
• Elxleben, Sömmerda district, Thuringia – close contacts since 1990

The municipality's arms might be described thus: Gules a saltire couped Or, in base a wheel spoked of six argent; Wheel of Mainz.

The municipality's economy was long dominated by winegrowing and fruit growing. Since the state capital is nearby, however, many commercial businesses have also been drawn to the municipal area. For example, a car's technical condition can be certified by the Gesellschaft für Technische Überwachung (“Company for Technical Inspection”, which is officially recognized in Germany as a certification body).

A tapping service is offered and for winemakers there is a big speciality shop for winery demands with unique expertise (more than 50 years) in sulphur dioxide handling. As the only German dealer in this field, the shop's stock runs the gamut of products from containers, accessories and duct components to volumetric metering systems.

• The municipality lies right near the Autobahn A 63 with its Klein-Winternheim (3) interchange.
• The Deutsche Bahn railway station Klein Winternheim-Ober Olm is in the community (Alzey–Mainz line).