There is ap ressing need to further increase the energy density of supercapacitors to meet the requirements of next-generation electronic devices.O ne promising solution is to develop advanced electrode materials with large capacitance at fast charge/discharge rates. Among the newly developed electrode materials for supercapacitors, iron oxides/hydroxidesh ave recently emerged as ap romising class of anode materials largely because of their attractive electrochemical performance,s ource abundance,l ow price, and environmental friendliness. However,t he use of these emerging materials in practical set-ups is unfortunately curtailed by their relativelys mall surface area and poor electrical conductivity,w hich could pose detrimental effects on their pseudocapacitive performance. Recently,material scientists and chemists in the energy community have attempted to address these materials'c hallenges by taking the advantage of the unique physical and chemical properties of iron oxides/hydroxides at the nanoscale size regime, which are the key topics discussed in this Focus Review.H ere, we first summarize recent advances in the developmento fh igh-performance iron oxide/hydroxide-based electrode materials, and their use as anode materials in asymmetric supercapacitors. We then highlight and exemplify several effective design strategies, such as architecturald esign, chemical modification, and multifunctional composites of iron oxide/ hydroxide-based electrodes, to further improvet heir electrochemicalp roperties. In the last section, we discuss the challenges and perspectivesi nt his exciting field, shedding some light on the design of iron oxide/hydroxide-based electrodes for practical applications.[a] Q.The ORCID identification number(s) for the author(s) of this article canbe found under http://dx.