The Yamaha DX7 is a synthesizer introduced by Yamaha Corporation in 1983. It was the first successful digital synthesizer and is one of the best-selling synthesizers in history, selling more than 200,000 units.

In the early 1980s, the synthesizer market was dominated by analog synthesizers. Frequency modulation synthesis, a means of generating sounds via frequency modulation (FM), was developed by John Chowning at Stanford University, California. FM synthesis created brighter, glassier sounds, and could better imitate acoustic sounds such as brass and bells. Yamaha licensed the technology to create the DX7, combining it with very-large-scale integration chips to lower manufacturing costs.

With its complex menus and lack of conventional controls, few learned to program the DX7 in depth. However, its preset sounds became staples of 1980s pop music; in 1986, it was used in 40% of the number-one singles on the US Billboard Hot 100. Its electric piano sound was particularly widely used, especially in power ballads. The English musician Brian Eno was proficient at programming his own sounds, and it was instrumental to his work in ambient music. Chips based on the DX7 sound chip, such as the YM2612, were used in technologies such as the Sega Genesis game console.

The DX7 was succeeded by FM synthesizers including the DX1, DX21, DX27 and DX100. In later years, its sounds came to be seen as dated or clichéd and its use declined.

By the mid-20th century, frequency modulation (FM), a means of carrying sound, had been understood for decades and was widely used to broadcast radio transmissions. In the 1960s, at Stanford University, California, John Chowning developed FM synthesis, a means of using FM to generate sounds that differed from subtractive synthesis. In 1971, to demonstrate its commercial potential, Chowning used FM to emulate acoustic sounds such as organs and brass. Stanford patented the technology and hoped to license it, but was turned down by American companies including Hammond and Wurlitzer. Chowning felt their engineers did not understand FM.

At the time, the Japanese company Yamaha was the world's largest manufacturer of musical instruments but had little market share in the United States. One of their chief engineers visited Stanford to view the technology. According to Chowning, "In ten minutes he understood ... I guess Yamaha had already been working in the digital domain, so he knew exactly what I was saying." Yamaha licensed the technology for one year to determine its commercial viability, and in 1973 its organ division began developing a prototype FM monophonic synthesizer, assisted by Chowning. In 1975, Yamaha negotiated exclusive rights for the technology.

Ikutaro Kakehashi, the founder of the Japanese company Roland, was also interested, but met Chowning six months after Yamaha had agreed to the deal. Kakehashi later said Yamaha were the natural partners in the venture, as they had the resources to make FM synthesis commercially viable.

Yamaha created the first hardware implementation of FM synthesis. The first commercial FM synthesizer was the Yamaha GS1, released in 1980, which was expensive to manufacture due to its integrated circuit chips. At the same time, Yamaha was developing the means to manufacture very-large-scale integration chips. These allowed the DX7 to use only two chips, compared to the GS1's 50. Yamaha also altered the implementation of the FM algorithms in the DX7 for efficiency and speed, producing a sampling rate higher than Stanford's synthesizers. Chowning felt this produced a noticeable "brilliant" sound.