statesman and chief executor of Chancellor Otto von Bismarck's (Bismarck, Otto von) free-trade policy for Prussia and then for imperial Germany. He entered government service in 1837 and in 1848 was transferred to the ministry of commerce. Realizing the influence of commerce on political union, Delbrück induced Hanover, Oldenburg, and Schaumburg-Lippe to join the Zollverein (customs union) by 1854; he convinced Austria to renew its trade relationship with the other German states in 1853.

With Bismarck's support, Delbrück began to apply the principles of free trade to Prussian fiscal policy, and in 1862 he concluded an important commercial treaty with France. He then successively became first president of the chancery of the North German Confederation (1867), Bismarck's representative on the federal tariff council (Zollbundesrat), and Prussian minister without portfolio (1868). In October 1870, when the union of Germany under Prussia became a practical possibility, Delbrück went on a mission to the South German states and contributed greatly to the Versailles agreements concluded in November. In 1871 he became head of the newly constituted Reichskanzleramt (Chancellery).

A strong advocate of free trade, Delbrück disagreed with Bismarck's later leanings toward protection and state control; he resigned, pleading ill health, in June 1876, after Bismarck introduced a plan for state acquisition of the railways. He later (1879) opposed in the Reichstag the new protectionist tariff and then retired from public life.