GaN-based lateral Schottky diodes (SBDs) have attracted great attention for high-power applications due to its combined high electron mobility and large critical breakdown field. However, the breakdown voltage (BV) of the SBDs are far from exploiting the material advantages of GaN at present, limiting the desire to use GaN for ultra-high voltage (UHV) applications. Then, a golden question is whether the excellent properties of GaN-based materials can be practically used in the UHV field? Here we demonstrate UHV AlGaN/GaN SBDs on sapphire with a BV of 10.6 kV, a specific on-resistance of 25.8 m{Omega}.cm2, yielding a power figure of merit of more than 3.8 GW/cm2. These devices are designed with single channel and 85-{mu}m anode-to-cathode spacing, without other additional electric field management, demonstrating its great potential for the UHV application in power electronics.