The article discusses the development of a fracture-resistant high-entropy alloy (CrMnFeCoNi) for cryogenic applications. The alloy exhibits exceptional mechanical properties, including high tensile strength (730 to 1280 MPa) and fracture toughness, which remain stable down to cryogenic temperatures (77 K). The alloy's fracture toughness at crack initiation exceeds 200 MPa·m^1/2, and it can sustain stable crack growth at cryogenic temperatures with a stress intensity above 300 MPa·m^1/2. The alloy's high toughness is attributed to its ability to maintain ductile fracture through microvoid coalescence, even at low temperatures. The study also highlights the importance of strain hardening and the presence of nanotwining as mechanisms that contribute to the alloy's excellent fracture toughness. The alloy's performance is compared with other materials, showing that it outperforms many pure metals and metallic alloys in terms of toughness, while maintaining comparable strength to structural ceramics and bulk-metallic glasses.The article discusses the development of a fracture-resistant high-entropy alloy (CrMnFeCoNi) for cryogenic applications. The alloy exhibits exceptional mechanical properties, including high tensile strength (730 to 1280 MPa) and fracture toughness, which remain stable down to cryogenic temperatures (77 K). The alloy's fracture toughness at crack initiation exceeds 200 MPa·m^1/2, and it can sustain stable crack growth at cryogenic temperatures with a stress intensity above 300 MPa·m^1/2. The alloy's high toughness is attributed to its ability to maintain ductile fracture through microvoid coalescence, even at low temperatures. The study also highlights the importance of strain hardening and the presence of nanotwining as mechanisms that contribute to the alloy's excellent fracture toughness. The alloy's performance is compared with other materials, showing that it outperforms many pure metals and metallic alloys in terms of toughness, while maintaining comparable strength to structural ceramics and bulk-metallic glasses.