Karl Konstantin Albrecht Leonhard Graf[a] von Blumenthal (30 July 1810 – 21 December 1900) was an officer of the Prussian Army and field marshal of the Imperial German Army, chiefly remembered for his decisive intervention at the Battle of Königgrätz in 1866, his victories at Wörth and Weißenburg, and above all his refusal to bombard Paris in 1870 during the siege, of which he was in command.

He was chief of the staff of the III Corps when, on the outbreak of the Second Schleswig War of 1864, he was nominated chief of the general staff of the army against Denmark, and displayed so much ability, particularly at Dybbøl and the night attack on the island of Als, which he masterminded and which ended the war, that he was promoted to major-general and awarded the order Pour le Mérite.

[1] In the Austro-Prussian War of 1866, von Blumenthal was Chief of Staff of the Second Army, commanded by the Crown Prince Frederick William.

At Königgrätz the crown prince said to him, "I know to whom I owe the conduct of my army", and von Blumenthal soon received promotion to lieutenant-general and the oak-leaves to the order Pour le Mérite.

Von Blumenthal's soldierly qualities and talent were most conspicuous in the critical days preceding the battle of Sedan, and his services in the war have been considered as scarcely less valuable and important than those of Moltke himself.

[1] Bismarck said: So far as one can see, the papers make no mention of him, although he is chief of the staff to the Crown Prince and, next after Moltke, deserves most credit for the conduct of the war.

He also directed the operations conducted by General von der Tann around Orleans, and defended the Grand Duke of Mecklenburg from interference by Moltke.