In this work we construct from ground up a homotopy theory of C * -algebras. This is achieved in parallel with the development of classical homotopy theory by first introducing an unstable model structure and second a stable model structure. The theory makes use of a full fledged import of homotopy theoretic techniques into the subject of C * -algebras.The spaces in C * -homotopy theory are certain hybrids of functors represented by C * -algebras and spaces studied in classical homotopy theory. In particular, we employ both the topological circle and the C * -algebra circle of complex-valued continuous functions on the real numbers which vanish at infinity. By using the inner workings of the theory, we may stabilize the spaces by forming spectra and bispectra with respect to either one of these circles or their tensor product. These stabilized spaces or spectra are the objects of study in stable C * -homotopy theory.The stable homotopy category of C * -algebras gives rise to invariants such as stable homotopy groups and bigraded cohomology and homology theories. We work out examples related to the emerging subject of noncommutative motives and zeta functions of C * -algebras. In addition, we employ homotopy theory to define a new type of K-theory of C * -algebras. for inspiring correspondence and discussions. We extend our gratitude to Michael Joachim for explaining his joint work with Mark Johnson on a model category structure for sequentially complete locally multiplicatively convex C * -algebras with respect to some infinite ordinal number [42]. The two viewpoints turned out to be wildly different. Aside from the fact that we are not working with the same underlying categories, one of the main differences is that the model structure in [42] is right proper, since every object is fibrant, but it is not known to be left proper. Hence it is not suitable fodder for stabilization in terms of today's (left) Bousfield localization machinery. One of the main points in our work is that fibrancy is a special property; in fact, it governs the whole theory, while left properness is required for defining the stable C * -homotopy category.