Atom interferometry offers the possibility of performing measurements of inertial quantities (acceleration and rotation) with sensitivities and accuracies that compete, and sometimes overcome, the levels of performance of "classical" sensors. I will introduce the principle of this technology and illustate its applications for gravity sensing. I will describe two different instrument geometries. The first one, and the most mature, is based on the use of free falling atoms as inertial proof masses, and allows to realize state of the art atomic gravimeters (and gradiometers). The second one, which uses atoms trapped in an optical trap, aims at performing local force measurements for fundamental tests of short range forces and Newtonian gravity.