The advent of two-dimensional materials with the possibility to vary their physical properties by means of doping, strain, electric, and magnetic fields allows to explore novel physical effects in the two-dimensional limit, where electronic, magnetic, and structural properties can be very different with respect to three-dimensional case. For example, the possibility to synthesize a two-dimensional superconductor will open the doors to new and unexplored applications in present nanotechnology. In this respect, reliable predictions of the superconducting critical temperature from first-principles and in real materials are important prerequisite to make important advances along this line of research. In this work, we review the results of recent theoretical predictions of superconductivity in experimentally realized two-dimensional superconductors: doped graphene and doped phosphorene. And for the latter system, we also present an analysis of several realistic dopants that could induce a superconducting state.