A 10-watt-level mid-infrared supercontinuum (SC) spanning 0.8-4.7 μm with ultra-high-power conversion efficiency is generated in a piece of fluoroindate (InF3) fiber. The pump laser is a master oscillator power amplifier system seeded by a mode-locked fiber laser operating at 1956 nm with pulse repetition rate and pulse duration of 33 MHz and 60 ps, respectively. A piece of InF3 fiber is fusion spliced to the output end of the pump light source with a low fusion splicing loss of 0.12 dB. An endcap made of multimode aluminum fluoride fiber is used to protect the fiber tip from possible optical or thermal damage. Benefiting from the fiber endcap as well as the low-loss splicing joint between silica and InF3 fiber, high-power SC generation is achieved with maximal output power of 11.3 W. Furthermore, the long wavelength edge of the obtained SC spectrum is extended to 4.7 μm. This Letter, to the best of our knowledge, not only demonstrates the first 10-watt-level SC generation in InF3 fibers, but also achieves record power conversion efficiency of 66.5% among reported 10-watt-level fluoride-fiber-based SC laser sources.