Mass transfer fundamentals in homogenous systems are discussed in this chapter. Important definitions are first introduced, and this is followed by a discussion of Fick’s first and second laws. Various simplifications of Fick’s laws are also discussed along with the various boundary conditions Encountered in engineering analysis. Methods are also described for estimating the solute diffusivity. There is then an extensive discussion on several classic solutions to Fick’s second law. This is followed by a definition of the mass transfer coefficient. Several examples are then discussed in detail to discuss how in some cases the mass transfer coefficient can be found through analytical solutions. The chapter ends with a summary of useful mass transfer coefficient correlations that can be used to solve a variety of mass transfer problems that are commonly found in engineering.