The non-perturbative functional renormalization group is a modern implementation of Wilson’s renormalization. It is based on an exact functional flow equation of a coarse-grained effective action (or Gibbs free energy). Its applications range from statistical physics and condensed matter to high-energy physics and quantum gravity, and include fields as diverse as turbulence, active matter, biological systems and neural networks. The school's courses will introduce the fundamentals of the non-perturbative renormalization group theory and present several applications.