Warner Music Group (WMG) is the third-largest of the big four major record labels, the others being Sony Music Entertainment, EMI, and Universal.

Warner Music Group also has a publishing arm, Warner/Chappell Music, that dates back to 1929, when Jack Warner, president of Warner Bros. Pictures Inc., founded Music Publishers Holding Company (MPHC) to acquire music copyrights as a means of providing inexpensive music for films. Among the historic compositions of which the publishing rights are controlled by WMG are the works of Cole Porter, Richard Rodgers and Lorenz Hart. Its printed music operation, Warner Bros. Publications, was sold to Alfred Publishing in 2005

WMG's roots in what became Time Warner date back to the founding of Warner Bros. Records as a division of the Warner Bros. movie studio in 1958, in reaction to one of its contracted actors, Tab Hunter scoring a hit for Dot Records, a division of Paramount Pictures. In 1963, Warner Bros. purchased Reprise Records, founded by Frank Sinatra three years earlier so that he could have more creative control over his recordings. Reprise was operated in conjunction with WBR.

After Warner Bros. was sold to Seven Arts Productions in 1967 (forming Warner Bros.-Seven Arts), it purchased Atlantic Records, now WMG's oldest label. For the next two years, Atlantic and its subsidiary label Atco Records were operated separately from WBR and Reprise.

In 1969, Warner Bros.-Seven Arts was sold to the Kinney National Company. Kinney (later to be known as Warner Communications) combined the operations of all of its record labels. The following year, Kinney bought Elektra Records and its sister label Nonesuch Records, and assembled the labels into a group known as Warner-Elektra-Atlantic, also called WEA for short, or Warner Music Group. The WEA name was also used as a label outside the U.S.

In the mid-1970s, WEA expanded by purchasing Asylum Records and Sire Records. The former was merged with Elektra to form Elektra-Asylum, though the separate names would still be used as well. The latter became a sublabel of WBR.

WEA's labels also distributed a number of otherwise independent labels. For example, Warner Bros. distributed Straight Records, DiscReet Records, Bizarre Records, Bearsville Records, and Geffen Records (the latter was sold to MCA in 1990). Atlantic Records distributed Swan Song Records.

In 1989, it was announced that Warner Communications was to merge with Time Inc. to form Time Warner, a transaction that was completed in 1990.

Atlantic started two new subsidiary labels in the early 1990s: EastWest Records (which absorbed Atco Records) and Interscope Records. The former was later absorbed into Elektra, and the latter was also sold to MCA in 1995.

Time Warner sold the company in 2004 to a group of investors led by Edgar Bronfman Jr. for US$2.6 billion, which was reportedly attempting to reduce its debt load. This spinoff was completed on February 27, 2004. In the 2004 transition to independent ownership, WMG hired record industry heavyweight Lyor Cohen from Universal Music Group (the result of the merger between the PolyGram and MCA label families) to attempt to reduce cost and increase performance. However, Time Warner may still have some ownership in WMG because its trademarks are not licensed by its former subsidiary. WMG's current logo is the former Warner Communications logo, although the ownership of the logo is still controlled by Time Warner.

On May 5, 2006, WMG apparently rejected a buyout offer from EMI. Then WMG offered to buy EMI and it also rejected the offer. In as of 2008, EMI was purchased by Terra Firma Capital Partners.

In 2006, also acquired Rykodisc (home of the Frank Zappa catalog) and Roadrunner Records.

On December 27, 2007, Warner announced that it would sell digital music without Digital Rights Management through AmazonMP3, making it the third major label to do so.

In 2007, Warner-Chappell sent a Cease and Desist letter to Walter Ritter, the creator of a freeware program called PearLyrics that was used to find lyrics of songs using the internet. In response to wide negative publicity, it subsequently apologised and offered to cooperate with him on the application. However, no subsequent overtures seem to have been made, and the software remains unavailable. In August 2008, Lyor Cohen sold 23 percent of his shares in the company.

In 2008, WMG, Universal Music, Sony BMG, EMI and the Indies (via Merlin) together with The Orchard licensed the full repertoire to the new concept of Spotify in order to fight piracy with a legal way of music streaming.

In 2008, WMG blocked a set of videos on Youtube, e.g. a video by Seanie B.This might have something to do with the breakdown of negotiations between Google and WMG. Although the blocked videos are not music videos, they might include WMG music in a minor way normally covered by Fair Use.

Since late 2008, WMG has continually pulled various other YouTube videos featuring music belonging to various bands and music labels, regardless of disclaimers. Many of these claims have included videos belonging to groups who are not signed with WMG.