Experimental review and prospects on leptonic $B^+$ decays
The leptonic $B^+$ decays are calculated in the Standard Model with great precision. Therefore it can be a very powerful probe of physics beyond the Standard Model. In this talk, we review experimental status of $B^+ \to \tau^+ \nu$, $B^+ \to l^+ \nu$ and other related decays. We discuss also future prospects with Belle II.