PourPy is an open-source Python package for generating thermodynamic stability diagrams of solid phases and complexes in aqueous electrolytes. These so-called Pourbaix diagrams provide valuable information about the reactivity of chemical elements and compounds as a function of the electrochemical potential and the pH. In the context of corrosion science, environmental and process engineering, Pourbaix diagrams are useful to predict the reactivity of aqueous complexes, the passivation behaviour of metals, and the electrochemical stability of the aqueous electrolyte. PourPy is a tool enabling users to inspect the reactivity of aqueous systems under full control of all chemical species considered. Users can define custom reactive systems containing multiple solid, aqueous and gaseous species thereof and build all (electro)chemical reactions to be considered. The package provides additional functionality to perform basic manipulations on the thermodynamic parameters associated with each chemical component, change the system's reference electrode as well as calculate the number of phases stable across a given potential-pH space or at discrete values.