This chapter presents the fundamental theory of steady one-dimensional premixed flames. The developments of the previous chapters are integrated here to understand the classical laminar premixed flame theory. The chapter starts with a phenomenological discussion, followed by the derivation of the one-dimensional conservation equations applied to the control volume of the flame. Proceeding in this manner it will be possible to understand the nuances of the analysis. Nevertheless, the one-dimensional equations could also be obtained from the more general expressions derived in Chap. 3 . Afterwards, the dimensionless forms of the one-dimensional equations are obtained by introducing characteristic physical quantities. The dimensionless numbers of Lewis, Zel’dovich, and Damköhler are introduced and discussed through examples. The chapter also discusses the analytical solution of the dimensionless conservation equations by using a Taylor series approximation to simplify the integration of the reaction rate term. Moreover, the chapter also introduces a more sophisticated model that accounts for detailed chemical kinetics and must be solved through numerical simulations.