Bookseller/Diagram Prize for Oddest Title of the Year

The Bookseller/Diagram Prize for Oddest Title of the Year, originally known as the Diagram Group Prize for the Oddest Title and commonly known as the Diagram Prize, is a humorous literary award that is given annually to a book with an unusual title. The prize is named after the Diagram Group, an information and graphics company based in London, and The Bookseller, a British trade magazine for the publishing industry. Originally organised to provide entertainment during the 1978 Frankfurt Book Fair, the prize has since been awarded every year by The Bookseller and is now organised by the magazine's diarist Horace Bent. The winner was initially decided by a panel of judges. However, since 2000x the winner has been decided by a public vote on The Bookseller's website.

Several controversies arisen since the creation of the awards, and there have been two occasions when no award was given because no titles were judged to be odd enough. Bent has complained about some of the winners chosen by the public; the 2008 winner, The 2009–2014 World Outlook for 60-milligram Containers of Fromage Frais, proved controversial because rather than being written by its listed author, Philip M. Parker, it was instead written by a machine of Parker's invention. The most recent winner, in December 2024, was The Philosopher Fish: Sturgeon, Caviar, and the Geography of Desire by Richard Adams Carey.