<p>Autistic people experience high rates of mental health conditions and resultant inpatient psychiatric admissions. Best practice guidance suggests that generic inpatient units are poorly suited to many autistic patients. This meta-analysis synthesised the highly variable empirical literature reporting the prevalence of autistic people in such settings. Systematic searches of three databases were conducted, with eighteen studies included in the final review. The pooled estimated prevalence was 10% (95% confidence interval: 6–14%), compared to a 1% prevalence of autism in the general population. Significantly higher prevalence was estimated for children (13%) vs. adults (4%). A structured risk of bias assessment suggested that the quality of studies was highly variable. High levels of heterogeneity were explored statistically. Despite best practice guidelines stating that many autistic people would have their needs best met in specialty units, autistic people are over-represented in generic psychiatric inpatient settings.</p>