We have been inundated with a wealth of fantastic photos after putting out an appeal for them on Facebook.
This gallery has been updated throughout the day as more and more pictures have been sent over!
MORE: Best World Book Day photos from 2021, World Book Day excitement grips Portsmouth as children become their favourite superheroes
Unfortunately due to the overwhelming amount of photos we were sent and time constraints, we have not been able to feature every single one sent to us today – despite hoping to be able to do so.
But we tried to feature as many as possible - and there are over 50 images in our gallery!
The gallery is at the bottom of this article – and make sure to click through all the pages!
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41. Gekko
Erin Harper, 4, dressed as Gekko from PJ Masks for World Book Day at St Pauls Catholic Primary School. Photo: Gemma Jenkins
42. A Ninja
Makai Moody, 5, from Portsmouth, went dressed as a ninja for World Book Day. Photo: Donna Huggins
43. Cat in the Hat
Lotti, 7, from Gosport, dressed as the Cat in the Hat for World Book Day. Photo: Dionne Cripps
44. Where's Wally
Jacob-Kanu, 13, from Havant dressed as Where's Wally for World Book Day. Photo: Hayley Smith