Fluorescent gold nanoclusters (AuNCs) have recently emerged as a novel kind of promising fluorescent probes for high-performance sensors and bioimaging because of their ultrasmall size (\3 nm), strong luminescence, good photostability, and excellent biocompatibility. Over the past decade, we have witnessed growing popularity of AuNCs in analytical applications and enormous efforts have been devoted to their development. In this review, we provide an update on recent advances in the development of AuNCs in terms of physicochemical properties, synthesis strategies, and bioapplications. The optical, electrochemical, catalytical, and solvatochromic properties of AuNCs are first summarized, which are followed by different ligands or template-assisted controllable synthetic methods. Afterwards functionalization of AuNCs is described in terms of ligand exchange, bioconjugation, and noncovalent interaction. We then focus on the applications of AuNCs as fluorescent probes for detection of metal ions, inorganic anions, small biomolecules, proteins, nucleic acids, drug molecules, pH, and temperature. We also summarize the usage of metal NCs in cellular and in vivo targeting and imaging. Finally, we conclude with a brief look at the future challenges and prospects of the development of AuNCs.