The paper investigates the opportunities and challenges of the application of ChatGPT in L2 learning classrooms. Since its first release, ChatGPT has fundamentally reshaped conventional perceptions of the capabilities attainable by large language models. One of its key applications is to assist L2 classrooms and facilitate L2 acquisition. The interactive conversational unique learning experience provided by ChatGPT in language classrooms largely changed the landscape of the traditional methods of language teaching and enriched the pedagogy study. Apart from opportunities brought by the chatbot, there are also challenges too. Although a large body of scholars has made endeavours in researching how to incorporate ChatGPT in L2 classrooms, most of the previous literature focuses on using ChatGPT to boost performance in particular tasks like writing or speaking, yet only a few have systematically discussed the opportunities and challenges to provide the big picture of the research in the field. This paper, therefore, provides a general review of both the opportunities and challenges brought by ChatGPT as a large language model in L2 teaching. It further points out some future directions that researchers might work on to make better utilisations of chatbots like ChatGPT and other similar NLP toolkits as well get a more insightful understanding of the issue.