The rapid development of additive manufacturing techniques, also known as three‐dimensional (3D) printing, is driving innovations in polymer chemistry, materials science, and engineering. Among current 3D printing techniques, direct ink writing (DIW) employs viscoelastic materials as inks, which are capable of constructing sophisticated 3D architectures at ambient conditions. In this perspective, polymer designs that meet the rheological requirements for direct ink writing are outlined and successful examples are summarized, which include the development of polymer micelles, co‐assembled hydrogels, supramolecularly cross‐linked systems, polymer liquids with microcrystalline domains, and hydrogels with dynamic covalent cross‐links. Furthermore, advanced polymer designs that reinforce the mechanical properties of these 3D printing materials, as well as the integration of functional moieties to these materials are discussed to inspire new polymer designs for direct ink writing and broadly 3D printing. New ink: Polymer designs for direct ink writing are outlined, with emphasis on strategies aimed at fulfilling the rheological requirements, reinforcing the mechanical properties, and integrating functional moieties (see figure).