Otto Didrik Schack, Count of Schackenborg (3 October 1810 â 26 July 1856) was a Danish aristocrat. He was the seventh holder of the Countship of Schackenborg from 1814 to 1856 with the title of enfeoffed count ().
Otto Didrik Schack was born on 3 October 1810 at Astrupgaard near Brøns in the Duchy of Schleswig. Born into the noble family of Schack, he was the eldest child and only son of the Danish nobleman and civil servant Hans Schack, and his wife Countess Louise Frederikke Lerche.
At the death of his father on 4 April 1814, he inherited the Countship of Schackenborg and assumed the title of enfeoffed count. As he was a minor, the countship was placed under administration until he came of age. In 1853 he was appointed chamberlain.
Count Schack died on 26 July 1856, aged just 45, in Flensburg in the Duchy of Schleswig. He was succeeded as Count of Schackenborg by his only child, Hans Schack.
Count Schack married firstly on 15 May 1842 in Tønder Friederike Rosine Juliane von Krogh, daughter of aristocrat and amtmann Frederik Christian von Krogh and countess Cornelia Sophie Lerche, by whom he had one son.
Count Schack married secondly on 5 June 1856 in Dänischenhagen Johanne Christiane Cornelia von Krogh, sister of his first wife.