In this contribution we review the motivations for, and recent advances in, new gate dielectric materials for incorporation into organic thin-film transistors (OTFTs) for organic electronics. After a general introduction to OTFT materials, operating principles, and processing requirements for optimizing low-cost organic electronics, this review focuses on three classes of OTFT-compatible dielectrics: i) inorganic (high-k) materials; ii) polymeric materials; and iii) self-assembled mono- and/multilayer materials. The principal goals in this active research area are tunable and reduced OTFT operating voltages, leading to decreased device power consumption while providing excellent dielectric/insulator properties and efficient low-cost solution-phase processing characteristics.