Otto Christian Hammer (18 August 1822 – 10 March 1892) was a Danish naval officer who participated in the First Schleswig War and the Second Schleswig War. After a successful campaign along the west coast of the Duchy of Schleswig in the First Schleswig War, Hammer became a lighthouse inspector but quit service with the navy only a few years later. When the Second Schleswig War broke out, Hammer enlisted again as an officer and lead a flotilla in the North Frisian Islands. Despite an early success against Austro-Prussian forces he was later captured by a hostile expeditionary corps.