The field of nonlinear Partial Differential Equations (PDEs) in Fluid Dynamics has seen tremendous scientific activity in the last decade, due to the facts that the underlying governing equations have a very rich and complex structure and that many of these equations still lack basic understanding concerning global existence and uniqueness of smooth solutions. The PDEs modeling and describing fluid flows play an important role in various areas of mathematics, natural sciences and also engineering. This special semester at CIRM will focus on nonlinear PDEs arising in incompressible fluid dynamics, such as Euler- and Navier-Stokes equations, geophysical flows, liquid crystals and complex fluids, non-homogeneous fluids and critical spaces. The semester will feature an international conference, a large research school for young researchers, a thematic workshop, research in pairs events and a program of invitations open to early graduate researchers as well as more senior guests.