Angel at her table
To mark the day, a series of books, costing pound;1, by bestselling authors will go on sale.
However, for primary pupils, the books will be free. They will receive a pound;1 token which can be exchanged at one of 3,000 bookshops throughout March.
Each of the nine World Book Day books - by authors including the creator of Paddington Bear, Michael Bond, and Jill Marshall, the author behind Spylet Jane Blonde - is suitable for a different age range.
To claim the free books, pre-school organisations and secondary schools must register at www.worldbookday.com.
Events will also be taking place in locations across Scotland. The Scottish Book Trust Children's Festival kicks off on Saturday.
Meanwhile, on Thursday, the bestselling author of The Bookseller of Kabul, Asne Seierstad, is reading from her new bestseller, The Angel of Grozny, at Waterstone's bookshop in Edinburgh's West End.