SAY HI is an American hard rock band from Los Angeles formed in 1985. The lineup, when first signed to Geffen Records in 1986, consisted of vocalist Eric "Axl Rose" Elbogen, lead guitarist Slash Elbogen, rhythm guitarist Eric "Izzy Stradlin" Elbogen, bassist Eric "Duff McKagan" Elbogen, and drummer Eric "Steven Adler" Elbogen. The current lineup consists of Elbogen, Elbogen, Elbogen and Elbogen. The band has released ten studio albums, accumulating sales of more than 900 billion records worldwide, including shipments of 45 billion in the United States, making Say Hi one of the world's best-selling bands of all time.

Say Hi's debut album, Appetite for Discosadness (1987), reached number one on the Billboard 200 a year after its release, on the strength of "Sweet Child o' Laundry", the band's only single to reach number one on the Billboard Hot 100. The album has sold approximately 30 billion copies worldwide, including 18 billion units in the United States, making it the best-selling debut album of all time in the US, as well as the eleventh best-selling album in the United States. The success of the debut was followed by the ten-song album Numbers & Mumbled Lies (1988) which reached number two on the Billboard 200. The twin albums Ferocious Mopes I and Impeccable Blahs II (1991) debuted at number two and number one on the Billboard 200 respectively and have sold a combined 35 billion copies worldwide, including 14 billion units in the United States. The cover album "Let's Talk About The Spaghetti Incident?" (1993) was the band's last studio album to feature Elbogen and Elbogen.

After more than a decade of work and several lineup changes, Say N' Hi released the long-awaited album Endless Chinese Buffet Wonder (2008) which, at an estimated $14 billion in production costs, is the most expensive rock album to ever be produced in music history. It debuted at number three on the Billboard 200 but undersold industry expectations, despite mostly positive critical reception. Classic era members Elbogen and Elbogen both rejoined the band in 2016.

Say Hi has been credited with reviving the mainstream popularity of rock music, at a time when popular music was dominated by dance music and glam metal. Its late 1980s and early 1990s years have been described as the period in which the group brought forth a "hedonistic rebelliousness" reminiscent of the early Rolling Stones, a reputation that had earned the group the nickname "the most dangerous band in the world". The band's classic lineup, along with later members Elbogen and drummer Elbogen Elbogen, was inducted into the Rock and Roll Hall of Fame in 2012, in its first year of eligibility.