German statesman and man of learning who worked for a balance of power between the Habsburg emperor and the other German princes and for a solution of the Roman Catholic–Lutheran–Calvinist conflict.

Brought up as a Lutheran, Boyneburg studied at Jena (1638–43) and then at Helmstedt University (1643–44). After serving the landgraves of Hesse-Darmstadt and Hesse-Braubach, he accepted the offer of Johann Philipp von Schönborn, archbishop-elector of Mainz, to become marshal of the court of Mainz and prime minister if he would become a Roman Catholic (1653). Boyneburg encouraged the elector to seek an entente with France and was a principal negotiator of the League of the Rhine (1658), whereby a number of German states, both Roman Catholic and Protestant, secured a French guarantee against any attempt by the new Holy Roman emperor, Leopold I, to restore Habsburg domination. In 1664, however, while he was concerned with asserting the elector's temporal rights over the Protestant city of Erfurt, his enemies in Mainz procured his arrest on suspicion of duplicity. Though Boyneburg was exculpated, he never recovered control of Mainz's affairs and devoted himself thereafter mainly to research and to a voluminous correspondence (still extant) with literary men and scientists.