Constantin von Tischendorf discovers the Codex Sinaiticus on his third visit to the Monastery of Saint Catherine, on Mount Sinai in Egypt. "The first two trips had yielded parts of the Old Testament, some from a rubbish bin. The emperor Alexander II of Russia sent him to search for manuscripts, which he was convinced were still to be found in the Sinai monastery."

The story of how von Tischendorf found the manuscript, which contained most of the Old Testament and all of the New Testament, has all the elements of a romance. Von Tischendorf reached the monastery on January 14; but his inquiries appeared to be fruitless. On February 4, he had resolved to return home without having achieved his goal. "On that day, when walking with the provisor of the convent, he spoke with much regret of his ill-success. Returning from their promenade, Tischendorf accompanied the monk to his room, and there had displayed to him what his companion called a copy of the Septuagint, which he, the ghostly brother, owned. The manuscript was wrapped up in a piece of cloth, and on its being unrolled, to the surprise and delight of the critic the very document presented itself which he had given up all hope of seeing. His object had been to complete the fragmentary Septuagint of 1844, which he had declared to be the most ancient of all Greek codices on vellum that are extant; but he found not only that, but a copy of the Greek New Testament attached, of the same age, and perfectly complete, not wanting a single page or paragraph." After some negotiations, von Tischendorf obtained the codex, and brought it to the Emperor Alexander, who fully appreciated its importance, and had it published in facsimile.

In 1933 the Russian government will sell the Codex Sinaiticus to the British Museum for 100,000 pounds.