RNA interference (RNAi) is a wondrous phenomenon that silences the expression of targeted genes via distinct messenger RNA degradation pathways. It has the potential as a therapeutic agent for variety of diseases, including viral infections, cancer, and immune diseases. RNAi mainly conducts gene regulation by 3 ways: microRNA, short hairpin RNA, and small interfering RNA. However, in vivo delivery of RNAi therapeutics is restricted because of charge density, molecular weight, and instability in the presence of nucleases. Furthermore, intracellular accumulation and endosomal escape have remained significant barriers in the delivery of these macromolecules. Many viral and nonviral delivery vectors have been thoroughly investigated to overcome these barriers. Researchers have found applications for RNAi in a variety of diseases and, hence, various delivery systems have been explored to satisfy the need. Both local and systemic strategies have been utilized to elicit RNAi's effect and each carries its own therapeutic implications with varying margins of safety. This review is an effort to describe the types of RNAi and their application in a variety of diseases using both local and systemic delivery approaches. It is sure that advancement in this direction will evolve a new landscape for treating a range of diseases.