The primary programming language used in machine learning is Python. Its simplicity and readability make it an ideal choice for both beginners and experienced developers. Python has a rich ecosystem of libraries and frameworks, such as TensorFlow, Keras, and scikit-learn, that provide powerful tools for building machine learning models. Its versatility allows for easy integration with other technologies and platforms, supporting tasks from data analysis to production deployment. The active community around Python also contributes to a wealth of resources and support, making it the go-to language for machine learning applications.