RNA interference (RNAi) offers programmable, sequence-specific silencing via small interfering RNA (siRNA) and microRNA (miRNA), but clinical translation hinges on overcoming instability, immunogenicity, and inefficient endosomal escape. This review synthesizes advances in non-viral nanocarriers-liposomes, polymeric nanoparticles, and extracellular vesicles (EVs)-that stabilize nucleic acids, tune biodistribution, and enable organ- and cell-selective delivery. We highlight design levers that now define the field: ligand-guided targeting, stimuli-responsive release, biomimicry and endogenous carriers, and rational co-delivery with small molecules. Across major disease areas-cancer and cardiovascular, respiratory, and urological disorders-these platforms achieve tissue-selective uptake (e.g., macrophages, endothelium, and myocardium), traverse physiological barriers (including the blood-brain barrier and fibrotic stroma), and remodel hostile microenvironments or immune programs to enhance efficacy while maintaining favorable safety profiles. Early clinical studies reflect this diversity, spanning targeted nanoparticles, local drug depots, exosome and cellular carriers, and inhaled formulations, e.g., and converge on core phase-I endpoints (safety, maximum tolerated dose, pharmacokinetics/pharmacodynamics, and early activity). Looking ahead, priorities include good manufacturing practice scale, consistent manufacture-especially for EVs; more efficient loading and cargo control; improved endosomal escape and biodistribution; and rigorous, long-term safety evaluation with standardized, head-to-head benchmarking. Emerging directions such as in vivo EVs biogenesis, theragnostic integration, and data-driven formulation discovery are poised to accelerate translation. Collectively, nanoparticle-enabled RNAi has matured into a versatile, clinically relevant toolkit for precise gene silencing, positioning the field to deliver next-generation therapies across diverse indications.