It was discovered in 1803 by William Hyde Wollaston in one such ore, and named for the rose color of one of its chlorine compounds.

The element's major use (consuming about 80% of world rhodium production) is as one of the catalysts in the three-way catalytic converters in automobiles.

White gold is often plated with a thin rhodium layer to improve its appearance, while sterling silver is often rhodium-plated to resist tarnishing.

Other uses of rhodium include asymmetric hydrogenation used to form drug precursors and the processes for the production of acetic acid.

[15] His procedure dissolved the ore in aqua regia and neutralized the acid with sodium hydroxide (NaOH).

[17] For decades, the rare element had only minor applications; for example, by the turn of the century, rhodium-containing thermocouples were used to measure temperatures up to 1800 °C.

Other rhodium(III) chlorides include sodium hexachlororhodate, Na3RhCl6, and pentaamminechlororhodium dichloride, [Rh(NH3)5Cl]Cl2.

This complex and related rhodium(II) trifluoroacetate have attracted attention as catalysts for cyclopropanation reactions.

When treated with triphenylphosphine, hydrated rhodium trichloride converts to the maroon-colored RhCl(P(C6H5)3)3, which is known as Wilkinson's catalyst.

Reduction of rhodium carbonyl chloride gives hexarhodium hexadecacarbonyl, Rh6(CO)16, and tetrarhodium dodecacarbonyl, Rh4(CO)12, the two most common Rh(0) complexes.

[32] Rhodium is one of the rarest elements in the Earth's crust, comprising an estimated 0.0002 parts per million (2 × 10−10).

Principal sources are located in South Africa, river sands of the Ural Mountains in Russia, and in North America, especially the copper-nickel sulfide mining area of the Sudbury, Ontario, region.

[37][38][39] The primary use of this element is in automobiles as a catalytic converter, changing harmful unburned hydrocarbons, carbon monoxide, and nitrogen oxide exhaust emissions into less noxious gases.

[36][40] In 2008, net demand (with the recycling accounted for) of rhodium for automotive converters made up 84% of the world usage,[41] with the number fluctuating around 80% in 2015−2021.

In the Monsanto process, rhodium iodides catalyze the carbonylation of methanol to produce acetic acid.

[43] This technology has been significantly displaced by the iridium-based Cativa process, which effects the same conversion but more efficiently.

Rhodium has also been used for honors or to signify elite status, when more commonly used metals such as silver, gold or platinum were deemed insufficient.

[49] Rhodium is used as an alloying agent for hardening and improving the corrosion resistance[25] of platinum and palladium.

These alloys are used in furnace windings, bushings for glass fiber production, thermocouple elements, electrodes for aircraft spark plugs, and laboratory crucibles.

For rhodium chloride, the median lethal dose (LD50) for rats is 198 mg (RhCl3) per kilogram of body weight.