To continue to improve integrated circuit performance and functionality, scaled transistors with short channel lengths and low thickness are needed. But further scaling of silicon-based devices and the development of alternative semiconductor channel materials that are compatible with current fabrication processes are challenging. Here we report atomic-layer-deposited indium oxide transistors with channel lengths down to 8.0 nm, channel thicknesses down to 0.50 nm and equivalent dielectric oxide thickness down to 0.84 nm. Due to the scaled device dimensions and low contact resistance, the transistors exhibit high on-state currents of 3.1 A mm–1 at a drain voltage of 0.5 V and transconductance of 1.5 S mm–1 at a drain voltage of 1.0 V. Our approach provides a promising alternative channel material for scaled transistors with back-end-of-line-processing compatibility. High-performance indium oxide transistors with dimensions smaller than advanced silicon technologies can be fabricated using an industry-compatible atomic layer deposition process.