  This thesis is devoted to the study of black hole solutions in ungauged
four-dimensional extended Supergravity. We characterize the most general
spherically symmetric and static black-hole solution of ungauged Supergravity,
and use the result to study the hidden conformal symmetries of Supergravity
black holes, obtaining the full Virasoro algebra of the dual conformal field
theory. We obtain also all the supersymmetric black-hole metrics of all
extended Supergravities using the properties of the groups of Type E7. We
introduce the H-F.G.K. formalism, which simplifies the construction of
non-supersymmetric black-hole solutions in N=2 Supergravity, and apply it to a
class of theories corresponding to Type-IIA String Theory compactified on a
Calabi-Yau threefold. As a result we obtain the so-called "quantum" black
holes, which only exist when certain quantum corrections (perturbative or
non-perturbative, depending on the solution) are included in the prepotential.
For the case of non-perturbative black holes, we elaborate on the potential
consequences of the appearance on the solution of multi-valued functions in
relation to the no-hair theorem for four-dimensional black holes. This thesis
also contains the relevant mathematical background to formulate extended
ungauged Supergravity in four-dimensions, that is, Special K\"ahler Geometry
and homogeneous spaces, as well as a brief introduction to the mathematical
structure of four-dimensional extended ungauged Supergravity.
