Teachers need to continually keep up with the ever-evolving language teaching and learning landscape brought by advancements in technology throughout their long careers. However, in actuality, they often receive little or no support from their institutions, which, consequently, leave them no choice but to learn on their own. In light of the current situation, it is not entirely unexpected that some teachers have been reaching out to online teacher communities formed on various social media platforms, including X and Facebook, which are easily accessible to virtually anyone as long as they have access to the internet, regardless of their location, work schedule, or financial situation. Hence, the present chapter aims to shed light into how these online teacher communities can be used as a professional learning source for teachers, particularly for those who are using technology for teaching purposes. It begins by giving a brief historical overview of online teacher communities, and drawing on well-cited studies predominantly conducted since the early 2010s. The benefits and challenges of teachers’ use of online teacher communities are then explored. The chapter ends with an outline of future research directions and predictions of what the future holds for online teacher communities.