Functional proteins in the cell are translated from the messenger RNA (mRNA) molecules, constituting less than 5% of the cellular transcriptome.The majority of the RNA molecules in the cell are noncoding RNAs, including rRNA, tRNA, snRNA, piRNA, lncRNA, microRNA, and poorly characterized circular RNAs (circRNAs). Recent studies established that circRNAs regulate gene expression by associating with RNA-binding proteins and microRNAs.With the growing understanding of circRNA functions, a subset of circRNAs has been reported to translate into proteins. Interestingly, the presence of Open Reading Frames (ORFs), N6-methyladenosine (m6A) modifications, and internal ribosomal entry sites (IRES) in the circRNA sequences indicate their coding potential through the cap-independent translation initiation mechanism. The purpose of this review is to highlight the mechanism of circRNA translation and the importance of circRNA-encoded proteins (circ-proteins) in cellular physiology and pathology. Here, we discuss the computational and molecular methods currently utilized to systematically identify translatable cir-cRNAs and the functional characterization of the circ-proteins. We foresee that the ongoing and future studies on circRNA translation will uncover the hidden proteome and their therapeutic implications in human health. This article is categorized under:RNA Methods > RNA Analyses in Cells Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs Translation > MechanismsCircular RNAs (circRNAs) are a special class of covalently closed noncoding RNA molecules without the 5 0 and 3 0 ends. Initially, circular RNAs (circRNAs) were discovered to be uncoated, infectious RNA molecules pathogenic to plants (Sanger et al., 1976). Soon after their discovery, the expression of circRNA was also confirmed in eukaryotic cells (Hsu & Coca-Prados, 1979). A few subsequent studies discovered misarranged exons and circRNAs in various samples (Capel et al., 1993;Cocquerelle et al., 1993;Nigro et al., 1991). However, they were thought to be accidental byproducts arising from splicing errors until the next-generation sequencing (NGS) technologies were developed. Recent NGS and Tanvi Sinha, Chirag Panigrahi, and Debojyoti Das contributed equally to this study.