Language learners need to develop speaking skills, which require abundant practice. However, authentic practice opportunities with diverse speakers are often limited, especially in foreign language contexts. Advances in natural language processing, automatic speech recognition, and artificial intelligence have led to the development of various spoken dialogue systems (SDS), such as Siri and Alexa, as well as SDS designed specifically for language learning. This entry reviews SDS technology and research, focusing on goal-oriented systems that enable multi-turn conversations. It discusses the design evolution from keyword-based systems to machine learning and Generative AI (GenAI), highlighting the benefits and challenges of using SDS for language learning and assessment.