Groot-Ammers is a town in the Dutch province of South Holland. It is a part of the municipality of Molenlanden, and is located about 13 km southeast of Gouda on the southside of the Lek River.
In 2001, the town of Groot-Ammers had 2822 inhabitants. The built-up area of the town was 0.56 km², and contained 1059 residences.
The statistical area "Groot-Ammers", which also includes the surrounding countryside, has a population of around 3100.