What is the King's Speech?


This may seem obvious but in British English it has a precise meaning which is slightly confused by the film title.  See this definition from the BBC

Written by the government and delivered by the reigning monarch, the Queen's Speech sets out the legislative agenda for the year ahead and is the centrepiece of the state opening of Parliament.
Each session of Parliament begins with this royal address and covers the following year.
In most years it takes place in November.
But every time there is a general election, Parliament is dissolved and the Queen's Speech takes place shortly after the government comes to power.
In the film the climax is a speech or address that the King gives rather than the King's Speech.