Cathinone (/ˈkæθɪnoʊn/; also known as β-ketoamphetamine) is a monoamine alkaloid found in the shrub Catha edulis (khat) and is chemically similar to ephedrine, cathine, methcathinone and other amphetamines. It is probably the main contributor to the stimulant effect of Catha edulis. Cathinone differs from many other amphetamines in that it has a ketone functional group. Other phenethylamines that share this structure include the stimulants methcathinone, MDPV, mephedrone and the antidepressant bupropion.

Khat has been cultivated in the Horn of Africa and Arabian Peninsula region of the world for thousands of years. It is most commonly chewed for the euphoric effect it produces. The active ingredient was first proposed in 1930, when cathine was identified as a predominant alkaloid in the plant. Cathine was thought to be the main active ingredient in khat until the 1960s, when it was found that the amount of cathine in the khat leaves is insufficient to produce the effects observed. In 1975, the United Nations Narcotic Laboratory analyzed khat leaves from Yemen, Kenya and Madagascar and found evidence of a different alkaloid, cathinone. Cathinone is molecularly similar to cathine, but is much more abundant in younger plants. This finding caused scientists to speculate that cathinone was the true active ingredient in khat.

A study was conducted in 1994 to test the effects of cathinone. Six volunteers who had never chewed khat were given an active khat sample and a cathinone-free placebo sample. The researchers analyzed the participants' moods, activity levels and blood pressure before and after consuming the khat or placebo. This analysis showed that cathinone produced amphetamine-like effects, leading the researchers to confirm that cathinone, not cathine, is the active ingredient in khat leaves.

Over 20 million people in the Arabian Peninsula and East Africa chew khat leaves daily. It is an important piece of the culture and economy in this region, especially in Ethiopia (where khat is said to have originated), Kenya, Djibouti, Somalia and Yemen. Men usually chew it during parties or other social gatherings while smoking cigarettes and drinking tea. Farmers and other workers also use khat in the afternoon to reduce fatigue and hunger as the day goes on. It functions like the caffeine in a strong cup of coffee as an anti-fatigue drug. Students and drivers have been known to use it to stay alert for longer periods of time.

In order to produce its desired effects, khat leaves should be chewed fresh. The fresh leaves have a higher concentration of cathinone. Waiting too long after cultivation to chew the leaf will allow the cathinone to break down into its less potent form, cathine. Because of the need for quick chewing, it is a habit that has historically been prevalent only where the plant grows. However, in the recent years with improvements in road and air transport, khat chewing has spread to all corners of the world.

The cultivation of khat in Yemen is a highly profitable industry for farmers. Khat plants will grow differently depending on the climate they are grown in and each one will produce different amounts of cathinone. It generally grows best in coastal, hot climates. In Yemen, the khat plant is named after the region in which it is grown. The Nehmi khat plant has the highest known concentration of cathinone, 342.5 mg/100 g.

Internationally, cathinone is a Schedule I drug under the Convention on Psychotropic Substances. Circa 1993, the DEA added cathinone to the Controlled Substances Act's Schedule I.

The sale of khat is legal in some jurisdictions, but illegal in others (see Khat (Regulation)). Substituted cathinones were also often used as the key ingredient of recreational drug mixes commonly known as "bath salts" in the United States.