Antiferromagnets having negligible net magnetization but a topologically nontrivial spin structure are a good testbed for investigating the intrinsic anomalous Hall effect (AHE). In this Letter, we explore L1 -ordered Mn Ir thin films, which are one of the noncollinear antiferromagnets predicted to exhibit the intrinsic AHE due to their topologically nontrivial spin structure. The anomalous Hall conductivity as large as σ = 40 ω cm was observed at R.T. This value can be translated to the anomalous Hall conductivity per net magnetization M as |σ /M| = 0.6 V , which is much larger compared to those for general ferromagnetic materials. We also show that σ depends on the crystallinity of Mn Ir as well as the chemical order parameter S characterizing a content of the L1 phase. Our results experimentally verify that L1 -ordered Mn Ir thin films exhibit the topologically originated AHE. 2 3 AHE AHE AHE 3 2 2 3 -1 -1 -1