Nikolai Iudovich Ivanov (Russian: Никола́й Иу́дович Ива́нов; 3 August [O.S. 22 July] 1851 – 27 January 1919) was a Russian artillery general in the Imperial Russian Army. In July 1914, Ivanov was given command of four armies in the Southwestern Front against the Austro-Hungarian army, winning a major battle of Galicia. During the Russian Revolution of March 1917, Tsar Nicholas II ordered Ivanov to suppress the revolutionaries but as promised reinforcements failed to come to his aid, he canceled the aborted mission. In 1917, he retired but a year later took command of the White Army. In 1919, Ivanov died of typhus in Southern Russia.

Ivanov's family origin was debatable, some sources say that Ivanov came from a noble family originated from the Kaluga Governorate, but other sources told that he was the son of a cantonist. Despite all of these sources about his family, the true identity of where his family originated from is still a mystery.

Ivanov was born on 22 July 1851 (based on the old calendar at use in the Russian Empire at that time), in Mosalsk in the Kaluga Governorate. He attended the 2nd Cadet Corps and the Pavlovsky Cadet Corps in St. Petersburg at an early age, and graduated from the Mikhailovsky Artillery School in 1869, and served in the 3rd Grenadier Guards and artillery brigades. He first saw action during the Russo-Turkish War (1877–1878), and was promoted to colonel in mid August 1877. After which he subsequently remained in Romania to serve as an instructor to the Romanian Army. In late July 1884, he was commander of the 2nd Battalion of the Imperial Guards Artillery, and in early April 1890, was appointed commandant of the fortress artillery of Kronstadt. In mid-December 1899, he was selected to be an aide-de-camp to Grand Duke Michael. He also participated in the suppression of the Boxer Rebellion in China during the beginning of the century, after which he was promoted to lieutenant-general in early December 1901.

General Ivanov participated in the Russo-Japanese War in 1904, he was appointed to the 1st Manchurian Army. In mid-July 1904, he was appointed commander of the Eastern Detachment, after its commander, Lieutenant General F. E. Keller was killed at the Battle of Motien Pass, and was later appointed to the 3rd Siberian Army Corps, and commanded the corps during retreating from Liaoyang after the battle ended. Later during the Battle of Shaho, he was ordered to bypass the left flank of the Japanese Army and repulse them back to Korea. After that, the Japanese retreated due to heavy resistance by the Russians. After that at Mukden, he distinguished himself during defending against the Japanese. After that brief success of his, he was awarded the Order of St. George both the 3rd and the 4th class for military distinction.

After the war, he became the commander of the Manchurian Army. In early November 1907, he became the commander of the 1st Army Corps. After that, he was appointed the chief of staff of the city of Kronstadt in mid-April of that year, and governor-general in November. Later that same year, he was appointed adjutant general. In mid April 1908, he was promoted to General of the Artillery; he was also appointed commander-in-chief of the Kiev Military District later in early December.

At the beginning of the First World War, Ivanov was appointed commander-in-chief of the Southwestern Front. At first, he together with the aged general Saltza suffered a minor defeat at Kraśnik, and Plehve with Evert lost the battle of Komarów; but success came next when his Russians made good progress into Austrian Galicia by winning the battles of Gnila Lipa and Rawa with the Russian casualties of about 200,000, the Austrians having roughly twice the casualties, including thousands of POWs. For the huge successes at the front, he was awarded the Order of St. Vladimir, 1st class with swords, and the Order of St, George of the 2nd degree, being three of the only generals that were awarded this high decoration, the other two generals being General Nikolai Ruzsky and Nikolai Yudenich. During the battle at the Vistula River, he with his Southwestern Front armies (4th Army and the 9th Army), together with the Northwestern Front commander-in-chief General Ruzsky with his armies (2nd Army and the 5th Army) from the North. In the matter of a month, General Ivanov and General Ruzsky's troops successfully repulsed the German advance, taking about a hundred kilometres of land. Later on, General Ivanov commanded an operation towards Kraków, it was successful at first, but was later ordered to retreat, ending the initial success.

In early 1915, General Ivanov gained approval of the Stavka to launch an offensive towards Hungary, but the offensive was disturbed by the Germans in Poland. Furthermore, the Austro-German forces launched an offensive in southern Poland. During the battle, the Russians suffered casualties up to 350 thousand men, and the Russians were pushed out of Galicia, starting the Russian Great Retreat. General Ivanov repeatedly showed examples of poor leadership of the troops and indecisiveness, much like many other Russian generals at that time. Most particularly, he and the General Radko Dimitriev (commander of the 3rd Army) didn't make any effort to strengthen the 3rd Army, which the Austro-German forces inflicted the main blow at and nearly wiping the army.

Later in June, General Ivanov ordered General Nikolai Khodorovich, commander-in-chief of the Kiev Military District, to take 1 in a 1000 local German civilians as hostages, and imprison them for the rest of the war. General Ivanov also prescribed to requisition that all the German hostages could only have a small portion of food of all the supplies they had got, and the hostages were settled in a highly secured residence. And if any hostages didn't follow the orders, they would be met with death penalty.