A tank is a simple freestanding container for a liquid or gas which is anchored to the ground and which does not rest on a pedestal. The most common shapes for this structural form are a cylinder and a sphere.

The container rests without a pedestal supporting it above the ground. Its contents can be liquid or gas, and its shape does not need to be cylindrical or spherical.

A water tower is an elevated water tank with a pressure-supply function. Elevation on a support distinguishes that form from the ground-anchored tank described here.