Eleven-year-old Euan from Lytham St Annes: "I have dressed up as Greg from Diary of a Wimpy Kid. Mum made the head herself out of papier-mâché"
Happy World Book Day, everyone!
The day is an annual celebration of authors, illustrators, books and reading, with events going on in more than 100 countries across the planet.
Thousands of you are going to school dressed as characters from your favourite books to join in with the World Book Day celebrations.
So we wanted to know who, or what, you are dressing up as this year...
Your amazing photos and comments
Here's Oliver, from Clacton-on-Sea, as the famous boy wizard Harry Potter
This is Amber from Kent as The Worst Witch's Mildred Hubble
Daviyah from London: "I dressed up as the Queen of Hearts from the book Alice's Adventures in Wonderland. It is one of my favourite books and films. My mum said I'm the Queen of her heart"
This is seven-year-old Imogen (right) and her five-year-old brother Fletcher. She said: "Here is my little brother and I as Willy Wonka and his Oompa Loompa. We are all ready for school, and are looking forward to celebrating World Book Day in style!"
Katie dressed up as Dr Seuss' The Cat in the Hat - and coat as it was cold at school this morning
Check out this brilliant Maud Spellbody outfit from six-year-old Sophie!
Ollie from Norfolk: "I'm dressing up as Nigel Nit-Boy from The World's Worst Children by David Walliams. His books are my favourite!"
Nell from Cumbria is The Worst Witch's Maud Spellbody
Jack from Evesham: "I'm dressed as Paddington Bear for World Book Day as he's one of my favourites"
Eleven-year-old Luke is Greg from Diary of a Wimpy Kid
Here's six-year-old James from Lincoln dressed as Wally
James from West Yorkshire: "I am at school today dressed as Grandpa from my favourite David Walliams book Grandpa's Great Escape"
Five-year-old Lewis from Kent is clearly a big Gruffalo fan!
Dexter from Weymouth: "I have dressed up as an Oompa Loompa from Charlie and the Chocolate Factory - I can't wait to show my friends at school!"
Six-year-old Andrew from Clydebank dressed up as Horrid Henry...
...while his older brother Alexander was Roald Dahl's Fantastic Mr Fox
Emily from Birmingham: "I'm Maud Spellbody from The Worst Witch and I think it's really cool!"
Darcey from Hertfordshire: "I'm dressing up as Zoe from Ratburger with Ratus on my head. I made my costume myself and also made Gingernut a grave and a ratburger to hold. I love World Book Day!"
Izzy from Derbyshire: "I have chosen Gangsta Granny as I love David Walliams' books. The costume was put together using things I found in the house apart from the wig and the mask!"
Here's 10-year-old Mya as Mary Poppins...
...and her sister Sofia is Gangsta Granny
Eight-year-old Isaac from Essex is Burt, a character created by author David Walliams for his Ratburger book
Two-year-old Leo's favourite books are the original Thomas the Tank Engine stories by Rev Wilbert Awdry
Eleven-year-old Sourish from King's Lynn: "Heat bones! I am a skeleton detective coming back to life! Skulduggery Pleasant!"
Ten-year-old Rhianna from South Shields: "I am Gangsta Granny by David Walliams"
Eight-year-old Archie is Newt Scamander from JK Rowling's Fantastic Beasts and Where to Find Them
Archie's younger brother, Ellwood, is Zog the dragon from the books by Julia Donaldson
Not to be outdone by her brothers, Archie and Ellwood (above), three-year-old Etta is the butterfly from The Very Hungry Caterpillar
Mildred Hubble from The Worst Witch is a very popular costume choice this year. Here's Minnie from Harrogate!
Eleven-year-old Charlotte from Swindon: "My mum calls me Mary Poppins, so that's who I have dressed up as! My school is having a book bingo and a short story writing competition."
Isobel from Gainsborough is a playing card inspired by the book Alice's Adventures in Wonderland
Five-year-old Maisie from Leamington Spa: "I am dressing up as Midnight the cat from The Worst Witch!"
Jessica from Wokingham: "I love Harry Potter and my favourite character is Hermione Granger - she is strong and clever!"
Charlotte helped to make her costume of Leaflette from Tom Blofeld's BeWILDerwood. Charlotte lives in Abu Dhabi, United Arab Emirates
Here's seven-year-old Grace from Cambridgeshire. She is going to school as Jemima from Isla Fisher's Marge in Charge
Lilly-Mac is in Wonderland today for World Book Day. Here's the six-week-old baby as Alice!
Eight-year-old Anna from Cambridgeshire is Polly from the Mr Gum books. She even has her own Jake the dog
Ten-year-old Holly from Chorley is dressed as Lottie the Lollipop Fairy!
Check out Amy from Surrey as Mildred Hubble from The Worst Witch, her favourite show. Bramble the dog had to stand in for Tabby the cat though!
Here are three-month-old twin sisters, Lucy and Freya. Their mum says they love The Very Hungry Caterpillar!
Ten-year-old Theo from Wirral: "This year I am dressing up as SpongeBob SquarePants. My mum and I worked together to make this outfit! It was really fun to make. I love reading books and my favourite author is Roald Dahl!"
Eight-year-old Martha from Wirral is Theo's sister: "I am dressing up as Matilda. I also have my fake pet lizard with me in the water bottle. All the things I needed we already had, so we didn't have to buy much. Matilda is my favourite book and movie. I heart it!"
Check out Evie from Walsall, who is David Walliams' Gangsta Granny. The costume was made by her mum. Good work!
Simarjot from Leicester: "I have dressed up as Princess Poppy from the film Trolls"
Ten-year-old Daniel's school are having a non-fiction book theme today. So he's decided to be one of England's most famous kings, Henry VIII!
Where's Wally? Summer from Edinburgh might have seen him
Olivia from Stoke loves Alice's Adventures in Wonderland by author Lewis Carroll. Here she is as the Mad Hatter
Eight-year-old Khadeeja from Leicester is going to school as Sophie from Roald Dahl's The BFG!
Ten-year-old Maryam from Leicester is dressed up as Miss Root from David Walliams' Demon Dentist book
Nine-year-old Reuben from Hampton: "I am Klaus Baudelaire from A Series of Unfortunate Events. I got all the bits for my costume myself from a charity shop and a fancy dress shop!"
Eleven-year-old Bailey from Manchester looks incredible as Peter Pan's shadow!
Daisy from Leicestershire is dressed up as Roald Dahl's Matilda
Eight-year-old Zara from York: "I am dressing up as Mildred Hubble from The Worst Witch. I love Mildred as she is such a good friend - even if it means she gets in trouble! I love World Book Day because I love books!"
Ten-year-old Aliyah, from Staffordshire, is dressed as Bellatrix Lestrange from Harry Potter with a homemade wand!
Six-year-old Joseph from Notts: "I am dressing as Willy Wonka! Charlie and the Chocolate Factory is one of my favourite books. Willy Wonka is creative, funny and really intelligent. He's an amazing character."
Nine-year-old Finley: "I'm dressing up as Harry Potter as he's my favourite book character and I love reading the books"
Freddie from Leicestershire is going to school as Roald Dahl's Fantastic Mr Fox
Ethan from Belfast: "I have dressed up as Hagrid from Harry Potter as I love all the books and I think Hagrid is a funny character. I helped my mum with the costume and I even have Hagrid's dog Fang"
Danna from Livingston looks wonderful as Willy Wonka from Roald Dahl's Charlie and the Chocolate Factory
Zachary from Liverpool is dressed as the sleepwalking Farmer Clegg, who wins the barnyard talent competition. Two-year-old Zachary loves story time and this is one of his favourite books
Brothers Caius and Edward have both been inspired by JK Rowling's Harry Potter books for World Book Day! Seven-year-old Caius (left) is Dobby the house elf and nine-year-old Edward is a mandrake plant
Eight-year-old Kiara from Surrey looks great as the Grinch from Dr Seuss' How the Grinch Stole Christmas
Seven-year-old Lucy, from Cheshire, loves The Worst Witch books and TV series. Her favourite character is Mildred Hubble, who she has dressed up as for World Book Day!
I'm dressing up as Hermione Granger - Josie, Prestatyn, Wales
I'm going as Mildred Hubble because I'm her biggest fan - Ruby-Lea, Blackpool, England
Aladdin - it's my favourite book. But I'm off sick so I can't wear my costume to school which I'm disappointed about - Toby, Crawley, England
I am not dressing up at my school but I am entering my school spelling bee - Sameeha, London, England
I am dressing up as Percy Jackson because it is one of my favourite books and I love modern and ancient history mixed together. I love World Book Day because you get to have free tokens to get £1 off books and we get to read books - Tulsi, London, England
I am going to be Miss Trunchbull as my favourite book is Matilda. Last year I was the White Witch from Narnia so you can probably tell I like to dress up as evil characters- Afeefa, London, England
For World Book Day I am dressing up as Hermione Granger from Harry Potter - Lily, England
I am dressing up as Mary Poppins - Rose, Derbyshire, England
I'm going as the Queen of Narnia and I like how wacky people's costumes can get and people get embarrassed - Anna, Warrington, England
I'm dressing up as Hermione because I love Harry Potter and I am a great fan of Emma Watson - Nia, London, England
I'm dressing up as Delia Gates from the Tom Gates books. I like the way she behaves and she makes me laugh! My daddy is making my costume with my help. I like that you don't have to go to school in uniform on World Book Day and can wear what you want - Maisy, Lancashire, England
I am going to be Ethel Hallow from The Worst Witch - Naomi, Edinburgh, Scotland
I am going to wear a Roman costume - Rayan, London, England