The $t\bar{t}$ production cross-section is measured in the lepton+jets channel using proton-proton collision data at a centre-of-mass energy of $\sqrt{s}=13$ TeV collected with the ATLAS detector at the LHC. The dataset corresponds to an integrated luminosity of 139 fb$^{-1}$. Events with exactly one charged lepton and four or more jets in the final state, with at least one jet containing $b$-hadrons, are used to determine the $t\bar{t}$ production cross-section through a profile-likelihood fit. The inclusive cross-section is measured to be ${\sigma_{\text{inc}} = 830 \pm 0.4 \text{(stat.)} \pm 36 \text{(syst.)}\pm 14 \text{(lumi.)} \mathrm{pb}}$ with a relative uncertainty of 4.6 %. The result is consistent with theoretical calculations at next-to-next-to-leading order in perturbative QCD.
