We develop a general-relativistic framework for two-component quantum dark fermion stars: equilibrium configurations of two degenerate fermion species governed jointly by gravity, a Yukawa-mediated dark fifth force, and a globally relevant Bohm quantum-pressure correction. The treatment retains the full covariant form of the nonlinear Klein–Gordon equation in the Schwarzschild interior, with closure relations valid at arbitrary compactness, from the ultralight baseline up to densities of order $0.16{\mathrm{fm}}^{-3}$ at which relativistic scalar densities and self-consistent effective fermion masses become unavoidable. Two Lagrangian parameters, the dark-fermion mass and the dimensionless ratio between the Yukawa channel and gravity, together fix the equilibrium structure; a joint measurement of mass and radius therefore constrains the dark-sector microphysics directly from gravitational-wave observables. For particle masses in the band ${10}^{-11}–{10}^{-10}\mathrm{eV}$, the configurations exhibit radii of 3–24 km and compactness in the range 0.14–0.34, behaving as dual mimickers: at moderate compactness they overlap with neutron stars in mass, radius, and inspiral frequency; at the most compact end ($\kappa \sim 0.34$, $R_T/R_S\simeq 1.5$) they cross the photon sphere and could masquerade as low-mass black holes in the mass-gap region. Tidal-deformability measurements discriminate against both populations simultaneously: the dimensionless tidal deformability is measurably smaller than the neutron-star value yet remains nonzero, unlike that of a genuine black hole. These objects populate the sensitivity bands of LISA, the Einstein Telescope, and Cosmic Explorer, producing astrometric microlensing signatures individually resolvable by Gaia. The framework thus provides a reproducible and falsifiable template for constraining dark-sector properties through multimessenger observations.

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• Astrophysical studies of gravity
• Particle dark matter