The former Weakest Link star joined the long-running letters and numbers quiz show last year, becoming its sixth presenter and the first female to take on presenting duties
She took over from The Apprentice’s Nick Hewer following his 10 year run at the helm.
Anne, who has fronted 265 episodes, revealed she had “stayed longer than I signed up for.”
“I’ve had a blast hosting this wonderful show. And I stayed longer than I signed up for,” she said.
“Now it is time for an older woman to take the reins.”
The 77-year-old star added that she hopes to have changed people’s perceptions on what older women are capable of.
“I hope too I’ve encouraged TV bosses to realise that not all women at the wrong end of their seventies are in care homes playing bingo and watching conjuring tricks,” she said.
“In fact the genius of Countdown is that it’s a brilliant way to keep the brain exercised. I run 5k most days of the week.
“And I can now do an anagram at twice the speed I could this time last year.”
Anne said she now plans to spend more time with her family and at her home in New York.
“I have grandchildren, a large garden and a home in New York, all deserving more of my attention,’ she said.
Anne will continue appear in shows until the summer. Channel 4 confirmed a new host will be announced soon.
A spokesperson for the channel said: “Quick-witted Anne has been a brilliant host on this iconic show.”
Anne followed in the footsteps of original host Richard Whiteley, who launched the show in 1982.
Des Lynam, Des O’Connor and Jeff Stelling have all also sat in the hot seat.
Since Anne joined the show in 2021, there have been persistent rumours in the press about her working relationship with the programme’s resident maths expert Rachel Riley.
Rachel admitted Anne was “not the cuddliest person in the world” amid reports of behind-the-scenes feuding but played down rumours of any on-set tension.
“You’ve got some women there and they want to make something up. I’ve seen the headlines of feuds escalating,” Rachel said last year.
The new mum then added: “I’ve been on maternity leave for about six to eight weeks.”
However, Rachel did go on to admit that her and Anne weren’t exactly best mates.
“[Anne’s] not the cuddliest person in the world,” she said. “But it’s just a different show now, she’s making it her own. She’s getting some stuff out of the contestants – sometimes it’s barbed, sometimes it’s funny, it’s just got a different flavour.”