An ex libris (Latin for 'from the books'), also known as a bookplate (or book-plate, as it was commonly styled until the early 20th century), is a printed or decorative label pasted into a book, often on the front endpaper, to indicate ownership. Simple typographical bookplates are termed "book labels".

Bookplates often bear a motif relating to the book's owner, such as a coat-of-arms, crest, badge, motto, or a design commissioned from an artist or designer. The name of the owner usually follows an inscription such as "from the books of..." or "from the library of...", or in Latin, "ex libris". Bookplates are important evidence for the provenance of books.

The most traditional technique used to make bookplates is burin engraving. The engraved copper matrix is then printed with an intaglio press on paper, and the resulting print can be pasted into the book to indicate ownership.

In the United States, bookplates replaced book rhymes (which replaced book curses) after the 19th century.

The earliest known marks of ownership of books or documents date from the reign of Amenophis III in Egypt (1391−1353 BCE).

However, in their modern form, they evolved from simple inscriptions in books which were common in Europe in the Middle Ages, when various other forms of "librarianship" became widespread (such as the use of class-marks, call numbers, or shelfmarks). The earliest known examples of printed bookplates are German, and date from the 15th century. One of the best known is a small hand-coloured woodcut representing a shield of arms supported by an angel, which was pasted into books presented to the Carthusian monastery of Buxheim by Brother Hildebrand Brandenburg of Biberach, about the year 1480—the date being fixed by that of the recorded gift. The woodcut, in imitation of similar devices in old manuscripts, is hand-painted. An example of this bookplate can be found in the Farber Archives of Brandeis University. In France the most ancient ex-libris as yet discovered is that of one Jean Bertaud de la Tour-Blanche, the date of which is 1529. Holland comes next with the plate of Anna van der Aa, in 1597; then Italy with one attributed to the year 1622. The earliest known American example is the plain printed label of Stephen Daye, the Massachusetts printer of the Bay Psalm Book, 1642.

The history of the bookplate as a symbolical and decorative print used to mark ownership of books begins in Germany. Bookplates are often of art historical interest. Albrecht Dürer is known to have engraved at least six copper plates (some quite large) between 1503 and 1516, and to have supplied designs for several others. Notable plates are ascribed to Lucas Cranach and to Hans Holbein, and to the so-called Little Masters (Masters of the small format—the Behams, Virgil Solis, Matthias Zundt, Jost Amman, Saldorfer, Georg Hupschmann and others). The influence of these draftsman over the decorative styles of Germany has been felt through subsequent centuries down to the present day, notwithstanding the invasion of successive Italian and French fashions during the 17th and 18th centuries, and the marked effort at originality of composition observable among modern designers. The ornate and elaborate German style does not seem to have affected neighbouring countries; but as it was undoubtedly from Germany that the fashion for ornamental bookplates spread, the history of German ex-libris remains relevant to all those who are interested in their development.

Printed ex-libris became common in France in the early 17th century. Until then, the more luxurious custom of blind- or gold-stamping a book's binding with a personal device had been more widespread: the supralibros. From the middle of the century, however, the ex-libris proper became quite popular; examples of that period are numerous and exhibit a complex design sensibility. The term "ex-libris", used as a noun (Exlibris (written in one word) in German) originated in France.