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ε-Fe₂O₃ nanoparticles embedded in a SiO₂ matrix have been synthesized by sol−gel chemistry and high temperature heat treatments. Virtually pure ε-Fe₂O₃ (in excess of 93%) is obtained, although a two-phase mixture, ε-Fe₂O₃ + α-Fe₂O₃, is observed for Fe₂O₃/SiO₂ ratios greater than 37 wt %. The ε-Fe₂O₃ nanoparticles are stable up to ∼1600 K. Optimized ε-Fe₂O₃ nanoparticles are ferrimagnetic, with a Curie temperature T_C ≈ 510 K, and remarkably high values of room-temperature coercivity, H_C = 20 kOe.