Résumé : Biofouling is a longstanding problem for biomedical devices, food storage, and marine equipment. Traditional antifouling strategies involve the use of biocidal agents, low surface-energy surface, and nanopatterned coatings. Recent studies show that hydrophilic surfaces are also promising for antifouling by directly reducing the adhesion of proteins and polysaccharides. However, it remains challenging to stably and conveniently coat nonadhesive hydrophilic polymers to various surfaces in high density. Especially, for marine antifouling, large-area painting of hydrophilic polymer coatings is susceptible to low adhesion strength, inhomogeneous surface coverage, and short durability. Here, a paintable antifouling hydrogel coating is proposed to overcome these limitations. An epoxy midcoat layer is introduced to provide both strong noncovalent adhesion to various surfaces and covalent linkages to hydrogel layers. The 3D hydrogel layers provide homogenous, relatively low Young's modulus and dense surface coverage and therefore shows outstanding antifouling properties toward various proteins, polysaccharides, seaweeds, and oil. Moreover, this hydrogel coating degrades slowly in sea water and facilitates the release of fouling biomolecules and organisms. Considering the great antifouling and fouling release properties, convenient coating processes, and high adhesion strength, this novel paintable antifouling hydrogel coating is anticipated to be broadly applicable for marine antifouling and other relevant fields.