Enzymes play a crucial role in all living organisms by accelerating the rates of a myriad of biochemical reactions that are necessary to sustain life. Although the vast majority of known enzymes are made of protein, in recent years it has become increasingly apparent that other molecular formats, like nucleic acids, can also serve in this capacity. DNAzymes (also known as deoxyribozymes) are synthetic enzymes made of short, single strands of deoxyribonucleic acid. These DNA-based enzymes offer the prospect of significant commercial utility, because they are exceptionally stable and can be produced very easily and inexpensively. The study of one particular DNAzyme, known as "8-17", has enhanced our understanding of DNAzyme-mediated catalysis. Moreover, the function of 8-17 has been regarded with special importance because it can catalyze sequence-specific cleavage of RNA, a reaction that has broad implications in biotechnology and biomedical fields. In this review, we explore the creation, characterization, and application of the 8-17 RNA-cleaving DNAzyme.