Little is known about how persons with autism spectrum conditions experience the process of learning foreign languages. To augment the research literature (reviewed here) with the experiences of autistic persons, online autism forums were scrutinised. Discussions pertinent to language learning were identified in English, Spanish, French and German, with 169 posts analysed. Thematic analysis revealed 8 themes. Three themes concerned ease and difficulty of learning. Reading and writing were strengths, due to their offline nature. Listening comprehension was difficult, especially with background noise. Speaking was difficult, due to demands of immediacy. Four inter-related themes could be understood as positive outcomes of autistic traits. Languages were a special interest, and many posters reported being self-taught. Posters often listed many languages but acknowledged that learning their full list was impractical. Posters reported being interested in diverse aspects of language structure, suggesting that languages were compelling because they provided an opportunity for systemising. Finally, posters discussed how autism conferred both advantages and disadvantages for language learning. Some posters discussed their engagement in terms reminiscent of polyglots and mild forms of linguistic savantism. This analysis revealed a group of curious learners whose abilities and strengths are mostly unknown to applied linguists.