Background: Electrical stimulation of the upper airway dilator muscles is an emerging treatment for obstructive sleep apnoea (OSA). Whereas invasive hypoglossal nerve stimulation (HNS) is an accepted treatment alternative to continuous positive airway pressure (CPAP), transcutaneous electrical stimulation (TES) may be a potential non-invasive alternative. Patients and Methods: A systematic review and meta-analysis (CRD42017074674) on the effect of HNS or TES on the apnoea-hypopnoea index (AHI) and the Epworth Sleepiness Scale (ESS) in OSA was conducted. Random-effects models were used. Heterogeneity and between study variance were assessed by I2 and τ2, respectively. Results: Of 41 identified clinical trials (n=1853), 20 (n=895) interventional trials could be pooled in the meta-analysis (15 HNS [n=808], 5 TES [n=87]). Middle aged (mean±SD 56.9±5.5years), overweight (body mass index, BMI 29.1±1.5kg/m2) patients with severe OSA (AHI 37.5±7.0h-1) were followed-up for 6.9±4.0month (HNS) and 0.2±0.4months (TES), respectively. The AHI improved by -23.5 (95% Confidence Interval, CI -27.0, -20.0) h-1 (p Conclusion: Invasive and transcutaneous electrical stimulation reduce OSA severity by a clinically relevant margin and improve associated symptoms.