Block books or blockbooks, also called xylographica, are short books of up to 50 leaves, block printed in Europe in the second half of the 15th century as woodcuts with blocks carved to include both text (usually) and illustrations. The content of the books was nearly always religious, aimed at a popular audience, and a few titles were often reprinted in several editions using new woodcuts. Although many had believed that block books preceded Gutenberg's invention of movable type in the first part of the 1450s, it now is accepted that most of the surviving block books were printed in the 1460s or later, and that the earliest surviving examples may date to about 1451.

They seem to have functioned as a cheap popular alternative to the typeset book, which was still very expensive at this stage. Single-leaf woodcuts from the preceding decades often included passages of text with prayers, indulgences and other material; the block book was an extension of this form. Block books are very rare, some editions surviving only in fragments, and many probably not surviving at all.

Some copies have added watercolour on the images, added either near the time of printing or later.

Block books are short books, 50 or fewer leaves, that were printed in the second half of the 15th century from wood blocks in which the text and illustrations were both cut. Some block books, called chiro-xylographic (from the Greek cheir (χειρ) "hand") contain only the printed illustrations, with the text added by hand. Some books also were made with the illustrations printed from woodcuts, but the text printed from movable metal type, but are nevertheless considered block books because of their method of printing (only on one side of a sheet of paper) and their close relation to "pure" block books. Block books are categorized as incunabula, or books printed before 1501. The only example of the block book form that contains no images is the school textbook Latin grammar of Donatus.

Block books were almost exclusively "devoted to the propagation of the faith through pictures and text" and "interpreted events drawn from the Bible or other sources in medieval religious thought. The woodcut pictures in all were meaningful even to the illiterate and semi-literate, and they aided clerics and preaching monks to dramatise their sermons."

Woodblock printing was invented in China sometime during the second half of the first millennium AD, but it is disputed as to whether or not woodblock printing in Europe was a native invention or came from China. Some believe it spread from the east while others believe it was independently invented in Europe.

There is no hard evidence that Chinese printing technology spread to Europe. However a number of authors have advanced theories in favor of a Chinese origin for European printing based on early references and circumstantial evidence. Tsien Tsuen-hsuin suggests that woodblock printing may have spread from China to Europe due to communications during the Mongol Empire era and based on similarities between blockprints in both areas. He suggests that European missionaries to China during the 14th century could have borrowed the practice of creating prints to be colored manually later on, which had been prevalent in China for a long time with Buddhist prints. The block books of Europe were produced using methods and materials similar to those in China and sometimes in ways contrary to prevailing European norms: European wood blocks were cut parallel with the grain in the same way as the Chinese method rather than the prevailing European practice of cutting across the grain, water-based ink was used rather than oil-based ink, only one side of the paper was printed rather than both, and rubbing rather than pressure was employed to leave the print. Robert Curzon, 14th Baron Zouche (1810 – 1873) held the opinion that European and Chinese block books were so similar in every way that they must have originated in China.

The question of whether printing originated in Europe or China was raised in the early 16th century by a Portuguese poet, Garcia de Resende (1470 – 1536). Paolo Giovio (1483 – 1552), an Italian historian who had come into possession of several Chinese books and maps through João de Barros (1496 – 1570), claimed that printing was invented in China and spread to Europe through Russia. Juan González de Mendoza (1545 – 1618) made similar claims about printing coming from China through Russia but also added another route through Arabia by sea and that it influenced Johannes Gutenberg. Several other authors throughout the 16th century repeated such statements.