This chapter is dedicated to applications of classical Newtonian gravity in the astronomical and astrophysical context. The main difference with respect to the role of gravity on earth is that, in the cosmos, the gravitational field is not constant, either in magnitude or in direction. This distinction is crucial and is rooted in the concept of self-gravity. We analyse both equilibrium and non-equilibrium properties of self-gravitating systems under the simplifying assumption of spherical symmetry.