Abstract: Phytophthora species cause several destructive diseases, including potato late blight, soybean Phytophthora root rot, pepper blight, and tobacco black shank. These diseases are currently controlled mainly with chemical fungicides; however, their long-term and repeated use can promote the development of fungicide resistance and increase the risk of pesticide residues. RNA interference(RNAi) regulates gene expression through small RNA-mediated, sequence-specific gene silencing and therefore provides a new strategy for the environmentally friendly management of Phytophthora diseases. Host-induced gene silencing(HIGS) relies on plants to produce small RNAs targeting essential genes of Phytophthora pathogens, thereby inducing gene silencing in the pathogen. Spray-induced gene silencing(SIGS), in contrast, induces pathogen gene silencing through the exogenous application of double-stranded RNA or small interfering RNA. This review summarizes RNAi systems in plants and Phytophthora species, as well as the mechanisms of cross-kingdom RNA transport, and reviews recent advances in the use of HIGS and SIGS for the control of Phytophthora diseases. Particular emphasis is placed on target gene selection, crosskingdom RNA transport and uptake, and RNA delivery systems, together with current limitations related to efficacy assessment, formulation stability, and biosafety. This review is intended to provide a theoretical basis for reducing dependence on chemical pesticides and developing precise and sustainable strategies for the management of Phytophthora diseases.