The fifteenth series of The Great British Bake Off began on 24 September 2024. Alison Hammond and Noel Fielding returned as hosts, with Paul Hollywood and Prue Leith returning to judge the series. The bakers competing in the series were announced on 17 September 2024.^[1]

The series was won by Georgie Grasso, with Dylan Bachelet and Christiaan De Vries finishing as the runners-up.^[2]

^[a] Jeff was ill and unable to compete during the technical challenge and showstopper in episode 1. As a result, the judges decided that it was unfair to eliminate anyone in his absence.
^[b] Jeff left the show during the technical challenge in episode 2 after feeling unwell.
^[c] Illiyin's showstopper in episode 2 was evaluated without her, as she fainted at the end of the challenge and required medical attention.

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The first episode is Cake Week.^[17] For the first challenge, the bakers were given two hours to produce an elevated version of their signature loaf cake. For the technical challenge, set by Paul, the bakers were asked to bake a batch of eight perfectly symmetrical mini Battenberg cakes, consisting of a light sponge sandwiched in a silky buttercream, coated in apricot jam and wrapped in marzipan. The bakers were given five minutes to inspect and taste a mini Battenburg cake with no additional recipe, and were then given two hours and fifteen minutes to complete the challenge. For the showstopper challenge, the bakers were asked to make a hyper-realistic illusion cake in four hours.

The second episode is Biscuit Week. For the first challenge, the bakers were given two hours to produce twelve Viennese whirls sandwiched in any shape, flavour, and filling of their choice. For the technical challenge, set by Prue, the bakers were asked to bake a batch of twelve mint cream biscuits, consisting of a buttery biscuit topped with a smooth peppermint cream and coated in tempered dark chocolate. For the showstopper challenge, the bakers were asked to make a biscuit puppet theatre with edible biscuit puppets.

^2 Jeff fell ill during the technical challenge and as it was his second consecutive week falling ill, he withdrew from the show altogether.
^3 Illiyin fainted at the end of the showstopper challenge. Since she was still able to complete the round, the judges continued with evaluating her bake, deeming her a candidate for elimination alongside Georgie and Hazel.

The ten remaining bakers were asked to carry out three challenges. The Signature Challenge was to make twelve identical savoury buns which had to be from an enriched, yeast-based dough, but could be any flavour and any shape. The Technical Challenge let the bakers watch Paul Hollywood demonstrate the plaiting of seven strands of dough to form a wreath before they then repeated the exercise. The final Showstopper Challenge this week was to make a cornucopia, also called a 'horn of plenty', filled with at least two different types of bread.

The nine remaining bakers tackled caramel this week throughout the three challenges. For the signature challenge, the bakers were asked to make 12 identical caramel biscuits. For the technical challenge, they were tasked with making a classic pear tarte tatin. For the showstopper, the challenge was to make a caramel mousse with at least two types of caramel.

The seven remaining bakers faced three challenges themed around autumn. For the signature, they had 2 hours and 45 minutes to make a decorative pie with autumnal flavours. The technical recipe was Prue Leith's vegan adaptation of a traditional parkin; the bakers had an hour and a half to complete the challenge. The showstopper required them to produce elaborate vegetable cakes themed around an autumn festival.

The six remaining bakers were tested on their dessert-making skills. The signature challenge was for eight mini meringue nests with two fillings, to be completed in two and a quarter hours. For the technical, Prue Leith tasked the contestants with making a traditional English pudding: the spotted dick. The showstopper asked the bakers to put their own spin on a classic Italian tiramisu; they had four and a half hours to complete this challenge.

In the quarterfinal, the five remaining bakers were given three retro challenges, taking them back to the 1970s. The signature required them to create a decorative stack of at least 30 profiteroles. The technical was Paul Hollywood's banoffee pie. Although the bakers were given ingredient measures, they did not have any instructions for how to make the pie. The showstopper challenge was to make a '70s-style tiered gateau.

Two specials were commissioned for the festive season:^[18]

The Great Christmas Bake Off featured soap opera stars Chris Bisson, Natalie Cassidy, Dean Gaffney, Shobna Gulati and Sheree Murphy.

The Great New Year Bake Off featured six Scottish bakers: Lea Harris from Series 1, Series 3 runner-up James Morton, Norman Calder from Series 5, Series 11 winner Peter Sawkins, Kevin Flynn from Series 13, and Nicky Laceby from Series 14.

The first episode of the 15th series was watched by 3.6 million viewers according to overnight figures, down from the 4.3 million of 2023.^[19]