Background: The transition from school to adult life is challenging for young people with intellectual disability. The study aimed to explore how young people with intellectual disability themselves experience the transition from school to adult life. Methods: A co-designed, qualitative study. Thematic data analysis of qualitative survey responses, semi-structured interviews, and focus groups with 27 young people with intellectual disability in three Australian states. Results: Participants found transition planning at school inconsistent or lacking and felt excluded from decision-making about their lives. Accessing meaningful services, training, and employment beyond volunteering was challenging and enduring, leaving participants in perpetual state of transition, feeling lost, and missing out of post-school adult milestones. Conclusions: Policy, system, and service gaps must be addressed with a nationally consistent and accountable approach that truly supports choice and control for young people with intellectual disability in transitioning from school into meaningful adult lives.