Real-time control-Tools is a novel software framework for modeling real-time control and decision support in water resources systems. It integrates different control paradigms ranging from simple feedback control strategies with triggers, operating rules and controllers to advanced optimization-based approaches such as model predictive control (MPC). A key feature of the package is the modular integration of modeling components, related adjoint models, and optimization algorithms which makes it well suited for the control of large-scale water systems. Interfaces enable its integration into Supervisory Control and Data Acquisition systems, operational stream flow forecasting, and decision support systems as well as hydraulic modeling packages. This paper presents an overview of the novel software framework, gives an introduction into the underlying control theory for which it has been developed and discusses the related software architecture. A first case describes an innovative combination of binary decision trees and feedback control in application to the modeling of a highly regulated River Rhine reach along the German–French border. Two additional cases present the efficient application of MPC to the short-term management of two large-scale water systems in the Netherlands and the USA.