The Gesture Recognition Toolkit (GRT) is a cross-platform, open-source, c++ machine-learning library that has been specifically designed for real-time gesture recognition. The GRT has been created as a general-purpose tool for allowing programmers with little or no machine-learning experience to develop their own machine-learning based recognition systems, through just a few lines of code. Further, the GRT is designed to enable machine-learning experts to precisely customize their own recognition systems, and easily incorporate their own algorithms within the GRT framework. In addition to facilitating developers to quickly create their own gesture-recognition systems, the machine-learning algorithms at the core of the GRT have been designed to be rapidly trained with just a few examples examples for each gesture. The GRT therefore allows a more diverse group of users to easily integrate gesture recognition into their own projects.