Hydrostatic pressure is, as the name indicates, pressure in a fluid (hydro: water in Greek) at rest (static). Pressure, by definition, is the continuous physical force exerted on or against an object by something in contact with (Simpson 1989). In the physical sciences, pressure is often defined as the perpendicular force per unit area. In this chapter, we will dissect the physics of hydrostatic pressure with examples of where hydrostatic pressure impacts nature, including biomechanics and human health. We will examine first what pressure is in a physical sense and use some mathematical equations to view it from multiple scientific and engineering disciplines.