Keith Julien University of Colorado Boulder This lecture is meant to provide an introduction to geophysical fluid flows with particular emphasis on the influence of rotation and stratification. It is aimed at a general audience of applied mathematicians. The talk will include a brief overview of the geophysical (and astrophysical) areas of interest highlighting the complexity of the observed dynamics and the multiscale nature of subject. The latter poses the key challenges for the fluid dynamics community and requires the development of idealized models with sufficient fidelity to capture the dynamics of interest. A review will be given of some classical approaches that result in asymptotically reduced models that take advantage of dominant balances that exist in geophysical flows. A primary limitation of such balanced models, however, is that they do not capture multiscale physics, an issue that will be addressed in the concluding part of the lecture.