The field of autonomous language learning in second language acquisition has experienced significant growth since its introduction by Holec in the 1980s. Several studies have explored how to promote learning autonomy in various spaces, including online learning environments. However, research related to autonomous language learning in online informal spaces is still ongoing. This dissertation aims to fill this gap by examining the role of online informal learning in promoting autonomous language learning, specifically focusing on how communities of autonomous language learners (CoALLs) empower and support their members to improve their learning autonomy and language proficiency. Additionally, it explores how fully autonomous language learners (FALLs) seek interaction online to enhance their second language proficiency. The dissertation consists of three studies: a literature review and two empirical studies. The literature review synthesizes research on autonomous language learning in online social spaces, analyzing articles published between 2010 and 2023. It identifies four major themes: language learning activities, learners' proficiency, anatomy of interaction, and learner affect, suggesting that informal online learning spaces benefit learner autonomy and language acquisition. The first empirical study explores CoALL dynamics, focusing on discussion topics, activities, and interactions. Findings suggest that CoALLs offer opportunities for instructional activities, peer collaboration, translanguage practice, competition, and professional development, motivating FALLs to participate actively. The second empirical study investigates FALLs' activities in digital spaces, using the individual network of practice (INoP) framework. It explores how FALLs use social media to seek interactions and facilitate language learning progression, revealing insights into their activities and INoP. The PRISMA framework guided the systematic literature review, comprising four stages: identification, screening, eligibility, and inclusion, to consolidate findings from various sources. Database searches were conducted using specific keywords to cover a 2010-2023 timeframe, yielding 945 studies. After screening titles, abstracts, and keywords, 57 articles were selected for full-text review, and 40 articles were ultimately included in the review based on established criteria. Meanwhile, for the empirical studies, the data were collected through interviews with members of the Facebook group Polyglot Indonesia, supplemented by analysis of group documents and artifacts. This study extends understanding of CoALLs and FALLs, highlighting how community-led regulations in informal spaces can create productive learning environments for FALLs. It also explores how individual choices in navigating online spaces influence autonomous language learning. The research underscores the value of informal online spaces for language learning, suggesting ways for educators and policymakers to integrate these aspects into formal education through peer collaboration, translanguage practice, and professional development. Policymakers could support online language learning communities by providing resources and incentives. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]