Nanopore electrochemistry refers to the promising measurement science based on elaborate pore structures that offer a well-defined geometric confined space to adopt and characterize single entities including single cells, single particles, and even single molecules by electrochemical technology. The electrochemical confined effect within the nanopore displays the ability to achieve single entity discrimination by focusing electron, photon, ion and magnetic fields into a small area. It converts the intrinsic properties of single entities into visible electrochemical read-outs with ultra-high temporal-spatial resolution. Therefore, the nanopore technology permits the possibility to resolve the transient signals for further revealing the single biomolecules dynamics. Nanopore electrochemistry has been applied in biophysics, chemical biology, disease diagnostics and other advanced disciplines by pushing the detecting limitation to molecular scale. In this book, we summarize the nanopore electrochemistry from the following three main areas. First, a nanopore-based single biomolecule sensing interface with chemical group precision is described in detail, including the design, instrumentation and advanced application. Then, the solid-state nanopore is summarized along with its fabrication process and application. Last, the glass nanopipette is introduced since it enables the monitoring of biomolecule interactions and the electron-transfer process in single living cells with high resolution and negligible cell damage. With the advent of advanced measurement mechanisms, instrumentation and data algorithms, the electrochemically confined nanopore is undoubtedly an exciting and promising field. We expect the next avenue for the wide application of nanopore electrochemistry in a variety of disciplines, leading us to explore the new chemistry at a much smaller scale.