Steven Siro Vai (; born June 6, 1960) is an American guitarist, composer, singer, songwriter, and producer. He was voted the 10th "Greatest Guitarist" by Guitar World magazine, and has sold over 15 million records. A three-time Grammy Award winner and fifteen-time nominee, Vai started his music career in 1978 at the age of 18 as a transcriptionist for Frank Zappa, and joined his band from 1980 to 1983. He embarked on a solo career in 1983 and has released eight solo albums to date. He has recorded and toured with Alcatrazz, David Lee Roth, Whitesnake, as well as having recorded with artists such as Mary J. Blige, Spinal Tap, and Ozzy Osbourne. Additionally, Vai has toured with live-only acts G3, Zappa Plays Zappa, the Experience Hendrix tour, as well as headlining international tours.
Vai has been described as a "highly individualistic player" and part of a generation of "heavy rock and metal virtuosi who came to the fore in the 1980s". The launch of the Ibanez JEM guitar developed and co-designed by Vai was described as the "exact moment the entire guitar landscape was reshaped". He also designed the first commercially produced seven-string guitar, the Ibanez Universe, which became popular among bands in various genres the 1990s, including nu metal, death metal, and progressive metal. He released his first solo album Flex-Able in 1984, while his most successful release, Passion and Warfare (1990), was described as "the richest and best hard rock guitar-virtuoso album of the ’80s".