Pre-registered protocol of a systematic review and meta-analysis evaluating the performance of constructed wetlands for the treatment and safe reuse of domestic and grey wastewater in hot drylands of Africa. The synthesis is structured around the redox continuum as a central design variable, with climate stratification by Köppen-Geiger classification and aridity index (CGIAR-CSI). Outcomes: abatement of nutrients (N, P), organic matter (BOD5, COD, TSS), pathogens (log reduction values), and emerging contaminants/ARGs. Compliant with PRISMA-P 2015, PRISMA-S, CEE v5; multilevel meta-analysis (metafor, log response ratio, robust variance); OHAT risk of bias and GRADE certainty. Inclusion criteria, exact search strings, and analysis plan locked before screening.