Abstract Carrier-free $${^{202}\textrm{Tl}}$$ 202 Tl was thermally separated from proton-irradiated $${^\textrm{nat}\textrm{HgO}}$$ nat HgO . Pressed $${^\textrm{nat}\textrm{HgO}}$$ nat HgO targets were irradiated with $$\approx {26}\,\textrm{MeV}$$ ≈ 26 MeV protons at the IP2 beamline of the high-intensity proton accelerator facility at the Paul Scherrer Institute. The well-known thermal decomposition of $$\textrm{HgO}$$ HgO at $$>{470}\,^\circ$$ > 470 ∘ C and the strong adsorption of $$\textrm{Tl}$$ Tl on a $$\textrm{Ta}$$ Ta surface allowed for a simple and quantitative gas-phase separation of carrier-free $$\textrm{Tl}$$ Tl from bulk amounts of $$\textrm{HgO}$$ HgO target material between 550 and $${670}\,^\circ$$ 670 ∘ °C. The separation efficiency was verified by $$\gamma$$ γ -spectroscopy via the main $$\gamma$$ γ -emissions of $${^{202}\textrm{Tl}}$$ 202 Tl and co-produced $${^{203}\textrm{Hg}}$$ 203 Hg . This method generally provides a fast and reliable preparation of carrier-free, neutron-deficient $$\textrm{Tl}$$ Tl radioisotopes (e.g., medically relevant $${^{201}\textrm{Tl}}$$ 201 Tl ) from a proton-irradiated $${^\textrm{nat}\textrm{HgO}}$$ nat HgO matrix.