Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental condition. Young people face challenges accessing ADHD healthcare in the UK, especially when transitioning between child and adult services. Digital health interventions (DHIs), as an adjunct to usual care, could improve access to healthcare information and condition-management support for this underserved group. This systematic review aimed to identify and synthesise evidence on DHIs suitable for young people aged 16-25 with ADHD, focussing on UK healthcare settings. We searched MEDLINE, Embase, PsycINFO, IEE Xplore, ACM Digital Library, Cochrane Database of Systematic Reviews and Cochrane Central Register of Controlled Trials, Scopus, Web of Science Core Collection, ProQuest Dissertations & Theses Global from inception to December 2023 for studies about DHIs for ADHD which provided healthcare and self-management information, and which included at least one participant aged 16-25 years. Studies were grouped by intervention type (healthcare & self-management information, symptom monitoring, and management tools), appraised using the Quality Assessment with Diverse Studies (QuADS) tool. A narrative synthesis was conducted. Nineteen papers representing 15 interventions and comprising 2651 participants were identified. Research studies spanned intervention development, feasibility/usability, pilots exploring preliminary effectiveness, and trials. QuADS scores ranged from 13 to 34 out of 39. Preliminary evidence of feasibility and acceptability was strongest for co-produced interventions. Limited evidence of effectiveness was found, except for psychoeducation DHIs which may be effective in reducing ADHD symptoms. Future research should build on this emerging evidence-base, emphasising co-produced DHIs tailored to young people with ADHD.