Measurements of semileptonic and leptonic beauty meson decays at Belle II

Three recent measurements of leptonic and semileptonic decays of $B$ mesons are presented here. All results use the full Belle II Run 1 $e^{+}{e}^{-}\to \mathrm{{\rm Y}}(4S)\to B\bar{B}$ dataset of 365 fb${}^{-1}$. We present one leptonic $B$ decay result: a measurement of the $B^{+}\to \tau \nu$ branching fraction with a hadronic tagging method; and two semileptonic $B$ decay results: a determination of $\mathrm{\mid }{V}_{cb}\mathrm{\mid }$ using $B\to D\mathrm{\ell }\nu$ decays with an inclusive tagging method and a test of lepton flavour universality with measurements of $\mathcal{R}\left(D^{+}\right)$ and $\mathcal{R}\left(D^{\ast +}\right)$ using semileptonic $B$ tagging.