Ontario is Canada's largest wine-producing province, with vineyards concentrated primarily in the southern regions near the Great Lakes. The province's wine industry centers around the Niagara Peninsula, which lies between Lake Ontario and Lake Erie, benefiting from the moderating influence of these large bodies of water. This region has established itself as Canada's most important wine-growing area, producing both table wines and specialized cold-climate wines.

The continental climate of Ontario's wine regions is significantly moderated by the Great Lakes, which help extend the growing season and protect vineyards from extreme temperature fluctuations. The Niagara Peninsula, designated as a Viticultural Area, features well-draining soils over limestone bedrock, with varied topography that includes the Niagara Escarpment. This geographic feature creates diverse microclimates and elevations that influence grape ripening and wine character throughout the region.

Ontario is particularly renowned for its icewine production, made from grapes that freeze naturally on the vine during winter months. Vidal Blanc has become a signature variety for icewine, alongside Riesling and Cabernet Franc. The province also grows cool-climate varieties such as Chardonnay, Pinot Noir, and Riesling for table wines. The extreme winter temperatures that can reach -15°C or lower create ideal conditions for producing authentic icewine, making Ontario one of the world's consistent producers of this specialized dessert wine style.