Karl Heinrich Ritter von Lang (7 June 1764 – 26 March 1835) was a German historian and statesman.
He was born at Balgheim, near Nördlingen. From the first he was greatly attracted towards historical studies, and this was shown when he began to attend the gymnasium of Oettingen, and in 1782, when he went to the university of Altdorf, near Nuremberg. At the same time he studied jurisprudence, and in 1782 became a government clerk at Oettingen. About the same period began his activities as a journalist and publicist.
But Lang did not long remain an official. He was of a restless, changeable character, which constantly involved him in personal quarrels, though he was equally quick to retire from them. In 1788 he obtained a position as private tutor in Hungary in family of Johann Calisius from Calish and Johanna Prónay in Bitsitz (today Bytčica, Slovakia), and in 1789 became private secretary to Baron von Buhler, the envoy of Württemberg at Vienna. This led to further travels and to his entering the service of the prince of Oettingen-Wallerstein. In 1792 Lang again betook himself to a university, this time to Göttingen. Here he came under the influence of the historian, Ludwig Timotheus Spittler, from whom, as also from Johannes von Muller and Friedrich Schlegel, his historical studies received a fresh impulse.
At intervals from 1793 to 1801 Lang was closely connected with the Prussian statesman Hardenberg, who employed him as his private secretary and archivist, and in 1797 he was present with Hardenberg at the Second Congress of Rastatt as secretary to the legation. He was occupied chiefly with affairs of the principalities of Ansbach and Bayreuth, newly acquired by Prussia, and especially in the settlement of disputes with Bavaria as to their boundaries.