This chapter provides an overview of Theory of Mind (ToM)—the ability to attribute beliefs, desires, intentions, and emotions to oneself and others—and examines its development, assessment, and variability in autism. Explanatory accounts are reviewed, including the mindblindness hypothesis, the role of executive functions, weak central coherence, and social motivation. Particular attention is given to language, both linguistic competence and multilingual exposure, as a scaffold for mental-state reasoning. This chapter distinguishes explicit, language- and executive function-dependent ToM tasks from implicit measures and considers why some autistic individuals succeed on structured tasks yet still struggle in spontaneous interaction. Intervention studies are surveyed, spanning executive function training, joint-attention training, and language-focused programs, as well as emerging technologies such as tablet-based and virtual reality platforms. While these approaches show promise, their generalization to everyday contexts remains inconsistent. Finally, critiques of ToM methodologies are addressed, including concerns about neurotypical bias and the importance of interactional perspectives such as the double empathy problem, which reconceptualize cross-neurotype difficulties as relational rather than unilateral differences.