This paper presents an ultrafast, one-step method for the continuous synthesis of high-entropy alloy (HEA) nanoparticles (NPs) directly from elemental metal powders using a high-temperature plasma jet. The method involves rapid heating and cooling of the metal mixtures to form HEA NPs with high efficiency and uniform composition. The study focuses on the synthesis of CrFeCoNiMo HEA NPs, achieving a production rate of 35 g h⁻¹ with a conversion efficiency of 42%. Thermofluid simulations reveal that the properties of HEA NPs can be tailored by adjusting the plasma gas, which affects the thermal history of the NPs. The synthesized HEA NPs exhibit excellent light absorption properties, with an absorptance of >96% over a wide spectrum, making them promising for photothermal conversion applications. The scalable and efficient synthesis method developed in this work represents a significant advancement towards industrial-scale production of HEA NPs.This paper presents an ultrafast, one-step method for the continuous synthesis of high-entropy alloy (HEA) nanoparticles (NPs) directly from elemental metal powders using a high-temperature plasma jet. The method involves rapid heating and cooling of the metal mixtures to form HEA NPs with high efficiency and uniform composition. The study focuses on the synthesis of CrFeCoNiMo HEA NPs, achieving a production rate of 35 g h⁻¹ with a conversion efficiency of 42%. Thermofluid simulations reveal that the properties of HEA NPs can be tailored by adjusting the plasma gas, which affects the thermal history of the NPs. The synthesized HEA NPs exhibit excellent light absorption properties, with an absorptance of >96% over a wide spectrum, making them promising for photothermal conversion applications. The scalable and efficient synthesis method developed in this work represents a significant advancement towards industrial-scale production of HEA NPs.