The Duchess of Cambridge will attend the BBC's Sports Personality award show in her first public engagement since leaving hospital for severe pregnancy sickness, St James' Palace said.
She will present the main award and lifetime achievement honour when Britain's top sports stars gather to celebrate a year of sporting achievement hailed as the nation's greatest ever.
The Duchess has not been seen in public since leaving the King Edward VII's Hospital in London on December 6.
She had received three days of treatment for a condition known as hyperemesis gravidarum, which leaves expectant mothers so ill they cannot keep food or liquids down.
Kate will attend the show in her role as an official ambassador of Britain's Olympic and Paralympic team, St James' Palace said.
A spokesman said: "The Duchess of Cambridge will tonight attend the BBC's Sports Personality of the Year awards at the ExCeL London, where Her Royal Highness will present the lifetime achievement and the main sports personality of the year awards.
"The Duchess will attend the event in response to a long-standing invitation from the BBC."
Kate, who is less than 13 weeks pregnant, was ordered by doctors to have a period of rest at her home at Kensington Palace after leaving hospital.
She was recently forced to miss two royal engagements - a Centrepoint Royal Albert Hall fundraiser and the British Military Tournament.
The Duke of Cambridge will not attend the event at London's ExCel centre as he remains in Anglesey in his role as an RAF search and rescue helicopter pilot, a St James' Palace spokesman said.