Riboregulators are small RNAs found in bacteria, archaea, plants, and fungi. They have a key part in the post-transcriptional regulation of gene expression. Riboregulators employ control at the RNA level, affecting processes such as initiation of translation, termination of translation, RNA splicing, and mRNA stability in either a cis- or trans-action state. They base-pair with a target mRNA to block or present the ribosome’s binding site or to initiate cleavage of the target RNAs. In eukaryotes, analogous systems are seen with noncoding RNAs that guide RNA-induced silencing complexes to complementary mRNA sequences to repress translation or induce degradation. Synthetic biology utilizes riboregulators to engineer gene circuits that respond to environmental or cellular signals. These engineered riboregulators often utilize riboswitches or toehold switches that change conformation upon binding a ligand molecule or another RNA, thereby turning gene expression on or off. Riboswitches and toehold switches can be programmed to execute various Boolean logic functions. Their high programmability and specificity make them valuable tools for gene regulation and biosensoring in both natural and engineered systems, driving progress in biotechnology, functional genomics, drug discovery, and synthetic biology.