The Mystery of the Sardine is a novel by Polish-English writer Stefan Themerson. Initially the novel was called Euclid was an Ass, named thusly for a tract written on Euclidean geometry by one of the characters. The manuscript came to the attention of the Dutch publisher De Harmonie, which had taken over Themerson's own Gaberbocchus Press, through which he had published his and his wife Franciszka's work, on a small scale. In 1985 a Dutch translation by Carol Limonard was published by De Bezige Bij. Through a Dutch-speaking person with connections to the English publisher Faber and Faber, it became published in English in 1986; Faber and Faber subsequently released more of Themerson's writing, including his last, (1988). The novel was republished by Dalkey Archive Press.