Robinson, 76, will be the sixth official Countdown host, following in the footsteps of Richard Whiteley, Des Lynam, Des O’Connor, Jeff Stelling, and Hewer.
The presenter is best known as the former host of the BBC game show The Weakest Link, which ran from 2000 to 2012.
Hewer, a former star of The Apprentice, had hosted the series for a decade. Robinson’s appointment was announced on the Channel 4 chat show Steph’s Packed Lunch.
On The Weakest Link, Robinson was known for her combative, withering repartee with contestants, and for her catchphrase: “You are the weakest link; goodbye.”