Grand Duke Nicholas Nikolaevich of Russia was a Russian general in World War I (1914–1918). The son of Grand Duke Nicholas Nikolaevich of Russia (1831–1891), and a grandson of Emperor Nicholas I of Russia, he was commander in chief of the Imperial Russian Army units on the main front in the first year of the war, during the reign of his first cousin once removed, Nicholas II. Although held in high regard by Paul von Hindenburg, he struggled with the colossal task of leading Russia's war effort against Germany, including strategy, tactics, logistics and coordination with the government. After the Gorlice–Tarnów offensive in 1915, Tsar Nicholas replaced the Grand Duke as commander-in-chief of the army. He later was a successful commander-in-chief in the Caucasus region. He was briefly recognized as emperor in 1922 in areas controlled by the White movement in the Russian Far East.

Grand Duke Nicholas Nikolaevich of Russia was the third son and sixth child of Tsar Nicholas I of Russia and Alexandra Feodorovna. He may also be referred to as Nicholas Nikolaevich the Elder to tell him apart from his son, Grand Duke Nicholas Nikolaevich of Russia (1856–1929). Trained for the military, as a Field Marshal he commanded the Russian army of the Danube in the Russo-Turkish War, 1877–1878.