Hydrogen (H 2 ) is an important clean energy carrier due to the merits of high combustion value and zero-carbon emission. Water electrolysis has been regarded as a promising technology for achieving green and sustainable production of H 2 . However, most of the electrocatalysts for water splitting can only work at low current density with poor long-term durability, and it is difficult to meet the extensive requirements of industrial-scale applications. In this article, challenges including the charge transfer, mass diffusion, and catalyst stability during high-current-density water electrolysis are discussed. With the aim of addressing these issues, various electrocatalyst design strategies including morphology engineering, electronic structure modulation, and surface/interface engineering are summarized in detail. For the purpose of promoting practical applications, recent achievements of practical anion exchange membrane water electrolysis (AEMWE) and proton exchange membrane water electrolysis (PEMWE) technologies are discussed. Finally, outlooks toward future investigations on high-current-density water electrolysis are presented. It is believed that this review will guide the rational design of catalysts with both high activity and high stability for high-current-density water electrolysis, and promote the development of industrial-scale green H 2 production. Challenges and design strategies of electrocatalysts for high-current-density water electrolysis.