The Bethmann family (/ˈbɛtmɑːn/; BET-mahn) has been remarkable for the high proportion of its male members who succeeded at mercantile or financial endeavors. This family trait began in medieval northern Germany and continued with the Bethmann bank, which Johann Philipp Bethmann (1715–1793) and Simon Moritz Bethmann (1721–1782) founded in 1748 and soon catapulted into the foremost ranks of German and European banks. Even after the bank's sale in 1976, there are Bethmanns engaged in commercial real estate and forestry in the 21st century.

The most notable of the Bethmanns was Simon Moritz von Bethmann (1768–1826), a banker, diplomat, politician, philanthropist and patron of the arts. His sister Maria Elisabeth was the mother of Marie d'Agoult and the grandmother of Cosima Wagner; his sister Susanne Elisabeth was the great-grandmother of Theobald von Bethmann Hollweg, who was chancellor of Germany from 1909 to 1917.

The Bethmann family, which produced the famous Bethmann banking dynasty, resided in Frankfurt am Main from the early 18th century onward. Earlier ancestors had come from the northern German town of Goslar. There – as burghers but not feudal nobility – the Bethmanns were among the upper crust of urban families. As such, they were entitled to delegate representatives to the town council and to bear a coat of arms; the earliest mention of the Bethmann name in Hanseatic Goslar – in the registrum parochianorum, a compendium on wax tablets of the town's parishioners – dates back to a Heinrich Bethmann in 1416. The surname "Bethmann" likely was an occupational name (like "Bäcker"/"Baker") given to collectors of the bede penninc, a tax requested (erbeten) from freemen in the Middle Ages.^{[citation needed]}

Subsequently, other Bethmanns – a Tile, a Bartold, a Hans and an Albrecht – appear in the records of Goslar, as owners of houses on Stonestrate and Korngasse, and as witnesses in the sale of houses. Another Tile buys a house on Knochenhauerstraße in 1492, serves on the town council, and is mentioned ten times between 1503 and 1520 as Munteherr, the title of an official responsible for minting of specie and weighing the metals produced from mining.

In 1512, Henning Bethmann, the great-great-grandfather of Konrad Bethmann, is accepted into the merchants' guild. In 1515, he is appointed Tafelherr, i.e. the councillor responsible for the town finances; this is followed by appointments to the posts of Munteherr in 1528, Kistenherr in 1538, and in 1548 supervisor of the vitriol works that extracted copper vitriol from ore. A Bartoldt Bethmann sold a house on Piepmäkerstraße in 1548 and another on Glockengießerstraße in 1566.

Henning's grandson Hieronymus is recorded in 1590 as a member of the merchants' guild; four years later, he married Ilsebey Drönewolf in St. Stephan's church. Hieronymus served as chairman of the merchants' guild, as Kornherr responsible for grain stocks, town councillor, member of the Sechsmann inner council and finally of the Neuer or governing council. Hieronymus died as the Swedes were entering Goslar. The town never fully recovered from the ransacking and pillaging of the Thirty Years' War, especially the three years of Swedish occupation.

Some of the 19th century literature incorrectly claimed that the family had originated in the Netherlands. The family assigned its archives in 1965 to the city of Frankfurt. The Bethmanns' archival materials occupy some 300 meters of shelf space, and the oldest document therein is a calligraphed agreement dated 29 May 1321, regulating traffic on the street between the Basler Hof property, which the Bethmanns purchased in 1762, and a neighboring house.

The Bethmann family's coat of arms can be traced to 1530. On the dexter side of a split shield, half an eagle in black is displayed against a golden background, while the sinister side displays two diagonal red bars against a silver background. At a later date, the motto tuebor (Latin for "I shall protect") was added.