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In this work, we show magnetic-moment-induced metal–insulator transitions in ThMnXN (X = As, P) and elucidate some of the experimentally observed results obtained by Zhang et al. through a first principles density functional study. Our calculations revealed that the magnetic ground states of ThMnXN (X = As, P) are C-type anti-ferromagnets with a small energy gap (∼0.4 eV) at the Fermi level, which is in good agreement with the experiments. Our constraint moment calculations revealed local magnetic moments of 3.42 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>μ</mi><mi>B</mi></msub></semantics></math></inline-formula> and 3.63 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>μ</mi><mi>B</mi></msub></semantics></math></inline-formula> in Mn atoms for ThMnAsN and ThMnPN, respectively, which are consistent with the experimentally measured local magnetic moment for Mn atoms. An effective Hubbard U = (U − J) of 0.9 eV was applied within the GGA+U formalism in ThMnPN to reproduce the experimental Mn moment. We also found that, as the Mn moments decrease in ThMnXN (X = As, P), the energy gaps also decrease and finally disappear at Mn moment 2.7 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>μ</mi><mi>B</mi></msub></semantics></math></inline-formula> for ThMnAsN and 2.8 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>μ</mi><mi>B</mi></msub></semantics></math></inline-formula> for ThMnPN. Therefore, our results stipulate a possible metal–insulator transition in ThMnXN (X = As, P) induced by the Mn local moment.