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We developed a novel high-performance L1₂-strengthened high-entropy alloy (HEA) in the multicomponent Ni-Co-Fe-Cr-Al-Nb system. The phase transformation, mechanical properties and associated deformation behaviors were systematically investigated through combinational analyses involving the three-dimensional atom probe tomography (3D-APT), transmission electron microscopy (TEM) and first-principles calculations. In contrast to conventional alloys that generally strengthened by Ni₃(Al, Ti)-type precipitates, a high density of coherent L1₂ nanoprecipitates with a new chemical constitution of (Ni, Co, Fe, Cr)₃(Al, Nb) can be controllably introduced via elaboratively tuning the content of Al and Nb, resulting in a large lattice misfit of ~0.78% that rarely achieved in previous HEAs. The newly developed (Ni₂Co₂FeCr)₉₂Al₄Nb₄ HEA enables excellent tensile properties at a large temperature window from room …