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We report the detection of H  i  21‐cm absorption from the   z = 2.289  damped Lyman α system (DLA) towards TXS 0311+430 with the Green Bank Telescope. The 21‐cm absorption has a velocity spread (between nulls) of ∼110 km s −1  and an integrated optical depth of . We also present new Giant Metrewave Radio Telescope 602‐MHz imaging of the radio continuum. TXS 0311+430 is unresolved at this frequency, indicating that the covering factor of the DLA is likely to be high. Combining the integrated optical depth with the DLA H  i  column density of  yields a spin temperature of   T  s = (138 ± 36) K , assuming a covering factor of unity. This is the first case of a low spin temperature (&lt;350 K) in a  z  &gt; 1 DLA and is among the lowest temperatures ever measured in any DLA. Indeed, the  T  s  measured for this DLA is similar to values measured in the Milky Way and local disc galaxies. We also determine a lower limit (Si/H) ≳ 1/3 solar for the DLA metallicity, amongst the highest abundances measured in DLAs at any redshift. Based on low‐redshift correlations, the low  T  s , large 21‐cm absorption width and high metallicity all suggest that the  z ∼ 2.289 DLA is likely to arise in a massive, luminous disc galaxy.

Discovery of 21‐cm absorption in a z abs = 2.289 damped Lyman α system towards TXS 0311+430: the first low spin temperature absorber at z > 1