The 61-year-old, who hosts the programme alongside Noel Fielding, said she is leaving in order to focus on other work projects.
Toksvig has fronted the programme alongside Fielding and judges Paul Hollywood and Prue Leith since 2017, after it moved to Channel 4 from BBC One.
But who could replace her? The bookies have already picked their favourites - and so have we...
Why did Sandi quit Bake Off?
Toksvig said she was stepping down to focus on other work projects - although the details of these are yet to be revealed.
"When stepping down from a job, it is quite common for people to say they are doing so in order to spend more time with their family," she said.
"Unusually I am departing from The Great British Bake Off so I can spend more time with my other work. As my waistline will testify, Bake Off is an all-consuming show.
"Spending time with Prue, Paul and Noel has been one of the great pleasures of my life. These are friendships which I know will continue beyond the confines of television.
Who could replace her? Seven stars who'd be perfect...
Julian Barratt is perhaps best known for his work on The Mighty Boosh back in the early '00s, alongside current GBBO presenter Fielding.
The Leeds-born funnyman and his comedy partner gained a cult following with their bizarre and surreal TV series, with Barratt's Howard Moon standing in stark contrast to Fielding's Vince Noir - and we think it would be absolutely brilliant to see these two working together again.
Viewers may also recognise Barratt, 51, for his work on Nathan Barley, Garth Marenghi's Darkplace and, more recently, for the Channel 4 critically acclaimed black-comedy Flowers.
Nadiya Hussain is a previous winner of the show, having taken home the crown on the sixth series of GBBO way back in 2015.
After winning Bake Off, Hussain went to have a successful broadcasting and food-writing career, presenting shows such as The Chronicles Of Nadiya, Nadiya’s British Food Adventure, Nadiya’s Family Favourites and Time To Eat.
The 35-year-old was also the co-presenter of The Big Family Cooking Showdown with Zoe Ball, has been a guest panellist on Loose Women and was invited to bake a cake for the Queen’s 90th birthday celebrations.
In 2017 she was named by Debrett’s as one of the 500 most influential people in the UK and was awarded an MBE in the New Year Honours for her services to broadcasting and to the culinary arts.
Another Channel 4 funnyman, Richard Ayoade will be best known for his work as the socially awkward Maurice Moss on sitcom The IT Crowd.
Like Barratt, Ayoade has also appeared in a number of cult comedy shows such as Garth Marenghi's Darkplace, Nathan Barley and The Mighty Boosh.
Viewers will also recognise him from his hilarious stints on Big Fat Quiz of the Year, Gadhget Man, Travel Man and his role as host on the revived Crystal Maze.
We think his typically sardonic, dry humour would work well on Bake Off, and of coursme his history of working with Fielding means they already have plenty of chemistry.
Former GBBO winner Candice Brown would be another great addition to the show. After winning the seventh series in 2016, Brown appeared on the 2018 series of Dancing On Ice and was partnered up with professional skater Matt Evers.
The ex-PE teacher occasionally appears on This Morning to cook, and briefly worked for Tom Kerridge before buying her own pub in Bedfordshire.
In January, the 35-year-old returned to the Bake Off tent for a New Year's special but missed out on being crowned star baker, as series eight runner up Steven Carter-Bailey triumphed.
In the same month, she also won Celebrity Mastermind with her specialist subject Audrey Hepburn.
The hugely busy Rylan Clark-Neal first rose to fame after finishing in fifth place in the ninth series of The X Factor.
After triumphing on Celebrity Big Brother, the 31-year-old presented spin-off Big Brother's Bit on the Side, landed a guest hosting job on This Morning and before returning to The Xtra Factor.
Clark-Neal is also host of the Supermarket Sweep revival along with It Takes Two, and will present new series of Ready Steady Cook in 2020.
Yes, his schedule is packed - but it's for a good reason. Surely he could squeeze one more programme in?
Extra Slice presenter Jo Brand would make a great addition to the GBBO line-up, where she could bring her hilarious presenting skills to the famous Bake Off tent.
The comedian is no stranger to our TV screens, having first appeared on the comedy circuit in the mid 1980s before making her first appearance on TV in the early 1990s.
More recently, the 62-year-old has appeared on a number of panel shows such as QI, Have I Got News for You and Would I Lie to You?.
The Birmingham funnyman is one of the UK's hottest comedians right now, and his effervescent brand of humour would go down well on in the Bake Off tent.
While he made his name on the stand-up circuit, the 31-year-old is also known for his may appearances on TV panel shows, such as Never Mind the Buzzcocks, QI, 8 Out of 10 Cats and Taskmaster.
And it a gig presenting one of Channel 4's top shows shouldn't be a problem for Lycett, who has hosted BBC's The Great British Sewing Bee since last year.
Everyone loved Liam Charles from series eight, didn't we? The Hackney-born baker was a fan favourite when he appeared on the show as a 20-year-old back in 2017.
And since his star turn in the Bake Off tent, Charles has gone on to add even more TV experience to his resume, having been presenting Bake Off: The Professionals alongside comedian Tom Allen since 2018.
In November of that year, Charles also presented the programme Liam Bakes on Channel 4, and the following year was even a judge alongside Prue Leith on Junior Bake Off.
The bookies' favourites
Here's a full rundown of the odds on who will replace Toksvig:
No one to replace her 2/1
Anna Richardson 4/1
Emma Willis 6/1
Sara Pascoe 6/1
Davina McCall 7/1
Gemma Collins 10/1
Susan Calman 10/1
Maura Higgins 12/1
David Mitchell 14/1
Jack Whitehall 16/1
Russell Brand 16/1
Emily Atack 18/1
Katherine Ryan 20/1
Clare Balding 20/1
Scarlett Moffatt 25/1
Maya Jama 25/1
Phillip Schofield 33/1
Ant McPartlin 50/1
Declan Donnelly 50/1