The Carrera Unified Formulation (CUF) was recently extended to deal with the geometric nonlinear analysis of solid cross-section and thin-walled metallic beams [1]. The promising results provided enough confidence for exploring the capabilities of that methodology when dealing with large displacements and post-buckling response of composite laminated beams, which is the subject of the present work. Accordingly, by employing CUF, governing nonlinear equations of low-to higher-order beam theories for laminated beams are expressed in this paper as degenerated cases of the three-dimensional elasticity equilibrium via an appropriate index notation. In detail, although the provided equations are valid for any one-dimensional structural theory in a unified sense, layer-wise kinematics are employed in this paper through the use of Lagrange polynomial expansions of the primary mechanical variables. The principle of virtual work and a finite element approximation are used to formulate the governing equations in a total Lagrangian manner, whereas a Newton-Raphson linearization scheme along with a path-following method based on the arc-length constraint is employed to solve the geometrically nonlinear problem. Several numerical assessments are proposed, including post-buckling of symmetric cross-ply beams and large displacement analysis of asymmetric laminates under flexural and compression loadings. the comprehensive review works by Carrera [2] and Kapania and Raciti [3,4], respectively. Nevertheless, among the fundamental topics in structural mechanics, the geometrical nonlinear analysis of elastic structures holds a relevant importance. It is a matter of fact that the effects of large displacements and rotations may play a primary role in the correct prediction, for example, of flexible beams, which continue to be employed for wing structures, space antennas, rotor blades, and robotic arms. The literature about this argument is large, and a detailed discussion on nonlinear formulations of composite structures falls outside the scope of this work. However, some relevant papers on nonlinear beam models are briefly outlined hereinafter for the sake of completeness.It is well known that for thin and solid cross-section beam structures, a good model for geometrically nonlinear analysis is represented by the so-called elastica [5,6,7]. The elastica beam addresses flexural problems by assuming the local curvature as proportional to the bending moment, according to the classical Euler-Bernoulli beam theory [8]. This assumption, of course, is too limiting for the analysis of composite structures, for which the shear effects may considerably alter the solution accuracy. For this reason, many works in the literature are based on the Timoshenko beam theory [9], which assumes a uniform shear distribution along the cross-section of the beam. In the domain of nonlinear analysis of metallic beams, this theory was extensively exploited; see for example the pioneering work of Reissner [10], who considered the effect of transverse force str...