From next month, the 50-year-old will front the BBC's political coverage alongside political editor Nick Robinson and James Landale, the deputy political editor.
Kevin Bakhurst, the controller of the BBC News channel and deputy head of the BBC newsroom, confirmed the appointment yesterday afternoon on Twitter.
Smith has reported from Westminster for the BBC since 1999, including the last 18 months spent as chief political correspondent for Radio 4, appearing regularly on the Today programme.
Despite being tipped as a rising star of BBC News, it was announced in June that Kuenssberg has decided to join ITV News as the broadcaster's new business editor, starting in September.
She is among a string of BBC News correspondents to have departed the corporation in recent months, including BBC World News anchor Matt Frei, who has moved to Channel 4 News.
Today, Channel 4 News also announced that Newsnight's Michael Crick is to become its new political correspondent, replacing Cathy Newman whe she becomes the programme's third main presenter.