The grass snake is widely distributed in mainland Europe, ranging from mid Scandinavia to southern Italy. It is also found in Middle East and Northwestern Africa. This species is one of only three snakes to occur in Great Britain, and is distributed throughout lowland areas of England and Wales; it is almost absent from Scotland and is not found in Ireland, which has no native snakes.
Grass snakes prey mainly on amphibians, especially the common toad and the common frog, although they may also occasionally eat ants and larvae. Captive snakes have been observed taking earthworms offered by hand, but dead prey items are never taken. The snake will search actively for prey, often on the edges of water, using sight and sense of smell. They consume prey live without using constriction.
Grass snakes are strong swimmers and may be found close to fresh water, although there is evidence individual snakes often do not need bodies of water throughout the entire season.
The preferred habitat appears to be open woodland and "edge" habitat, such as field margins and woodland borders, as these may offer adequate refuge while still affording ample opportunity for thermoregulation through basking. Pond edges are also favoured and the relatively high chance of observing this secretive species in such areas may account for their perceived association with ponds and water.
Grass snakes, as with most reptiles, are at the mercy of the thermal environment and need to overwinter in areas which are not subject to freezing. Thus, they typically spend the winter underground where the temperature is relatively stable.