Bernhard Heinrich Karl Martin, Prince of Bülow (German: Bernhard Heinrich Karl Martin Fürst von Bülow [fɔn ˈbyːloː]; 3 May 1849 – 28 October 1929) was a German politician who served as the imperial chancellor of the German Empire and minister-president of Prussia from 1900 to 1909. A fervent supporter of Weltpolitik, Bülow devoted his chancellorship to transforming Germany into a global power. Despite presiding over sustained economic growth and major scientific breakthroughs within his country, his government's bellicose foreign policy did much to antagonize France, Great Britain and Russia thereby significantly contributing to the outbreak of World War I.

Born into a prominent family of Danish-German aristocrats, Bülow entered the German foreign service after his father, Bernhard Ernst von Bülow, was appointed foreign secretary in Otto von Bismarck's government. He held several diplomatic posts, including German ambassador to Rome, before being appointed foreign secretary in 1897 by Wilhelm II. Three years later, he was appointed chancellor following the resignation of the Prince of Hohenlohe.

As chancellor, Bülow promoted cautious and conservative domestic policies while pursuing an ambitious and expansionist policy in foreign affairs. His open challenge to France's growing control over Morocco sparked the First Moroccan Crisis, which aggravated the French and the British and helped strengthen the Entente Cordiale. In 1908, Wilhelm's indiscreet remarks were published during the Daily Telegraph Affair, causing significant damage to German foreign relations and the Kaiser's prestige. Bülow was blamed for failing to prevent the blunder and, having lost the support of both the Kaiser and the Reichstag, he resigned in 1909 and was succeeded by Theobald von Bethmann Hollweg.

Bülow moved to Rome after his resignation. He came out of retirement in late 1914 to serve as interim ambassador to Italy, but was unable to bring King Victor Emmanuel III to the side of the Central Powers. Bülow died in Rome in 1929 at the age of 80.

He was born at Klein-Flottbeck, Holstein (now part of Altona, Hamburg). His father, Bernhard Ernst von Bülow, was a Danish and German statesman and member of an old House of Bülow, while his mother was a wealthy heiress, Louise Victorine Rücker (1821–1894). His brother, Major-General Karl Ulrich von Bülow, was a cavalry commander during World War I. Bülow attributed his grasp of English and French to having learnt it from governesses as a young child. His father spoke French, and his mother spoke English, as was common in Hamburg society.

In 1856, his father was sent to the Federal Diet in Frankfurt to represent Holstein and Lauenburg, when Otto von Bismarck was also there to represent Prussia. He became a great friend of Bismarck's son Herbert when they played together. At 13, the family moved to Neustrelitz when his father became Chief Minister to the Grand Duke of Mecklenburg, where Bernhard attended the Frankfort gymnasium, before attending Lausanne, Leipzig, and Berlin Universities.

He volunteered for military service during the Franco-Prussian War and became a lance-corporal in the King's Hussar Regiment. In December 1870, the squadron was in action near Amiens, and he later described charging and killing French riflemen with his sabre. He was promoted to lieutenant and was invited to remain in the army after the war but declined. He completed his law degree at the University of Greifswald in 1872. Afterwards, he entered first the Prussian Civil Service and then the diplomatic service. His religion was Lutheran.

In 1873 his father became State Secretary for Foreign Affairs in the German government, serving under Bismarck. Bülow entered the diplomatic corps. His first short assignments were to Rome, St. Petersburg, Vienna and then Athens. In 1876, he was appointed attaché to the German embassy in Paris, attended the Congress of Berlin as a secretary and became second secretary to the embassy in 1880.