This book is devoted to the nonlinear buckling of spherical shells under uniform external pressure. Such shells take the form of complete sphere, opening sphere, hemi sphere, spherical cap, multi-segment sphere, and tori-sphere. Experimental, analytical, and numerical approaches are implemented to perform the research. The work is intended for the professional researchers, teachers, and students whose research interest involves the instability of pressure vessels in civil, aero, and ocean engineering, as well as the corresponding technological staffs.