This is the third school on Advances in Complex Systems. The first edition of the school took place in the summer of 2015 and the second edition in the summer of 2017. The scope of the school series is to present recent advances in complex systems discussing applications of statistical mechanics of non-equilibrium and disordered systems, theories of complex networks and other stochastic systems to different topics in materials science, social sciences, biology and biomedical research. The broad choice of interdisciplinary topics is designed to expose the students to some of the multiple facets of complex systems theory. The 2019 edition of the school will focus on inderdisciplinary and quantitative approaches that span from ecology to economics. The school is open to 40 graduate students and postdoctoral fellows working in complex systems and related fields.