Megumi Hayashibara is a Japanese singer, lyricist, and music artist whose career is deeply intertwined with anime productions, having performed theme songs and character image songs for numerous series since the late 1980s. Her musical identity is defined by a prolific output of singles and albums, many of which served as opening or ending themes for popular television series, films, and original video animations.

Hayashibara's extensive discography includes thirteen studio albums, five compilation albums, two EPs, and thirty-seven singles. Her early studio albums established her presence in the music industry, with releases such as Half and, Half (1991), Whatever (1992), Perfume (1992), SHAMROCK (1993), SpHERE (1994), Enfleurage (1995), bertemu (1996), Iráváti (1997), Fuwari (1999), feel well (2002), Center Color (2004), Plain (2007), and Choice (2010). She also released the compilation albums Vintage S and Vintage A in 2000.

A significant portion of Hayashibara's musical work is directly connected to the Slayers franchise. She performed the opening theme Get Along as a duet with Masami Okui for the first television series, and subsequently performed the opening themes Give a Reason for Slayers NEXT, Breeze for Slayers TRY, Plenty of Grit for Slayers Revolution, and Front Breaking for Slayers Evolution-R. Her contributions to Slayers also include numerous ending themes and songs for films and original video animations. The song Don't Be Discouraged was released as a single on April 23, 1997, serving as the ending theme for Slayers Try. The single also contained the B-side Breeze, which was used as the series' opening theme, and reached number four on the Oricon weekly chart. Other Slayers-related songs include Midnight Blue from the first motion picture, Just Be Conscious from Slayers Return, Reflection from Slayers Great, Raging Waves from Slayers Gorgeous, and feel well from Slayers Premium.

Hayashibara's work on Neon Genesis Evangelion is particularly notable for her performances of the classic standard Fly Me to the Moon. Multiple versions of the song featuring her vocals were used as ending themes for various episodes of the television series, including the Rei #23 Version, Rei #25 Version, and Rei #26 Version as specified by the user. A compilation album titled The Birthday of Rei Ayanami, released on March 30, 2001, featured Hayashibara performing the Ayanami Version of Fly Me to the Moon, as well as a new mix of the opening theme A Cruel Angel's Thesis. She also contributed to the album Evangelion Finally, released in 2020, which includes the AYANAMI version of Fly Me to the Moon among other tracks.

Beyond these franchises, Hayashibara has an extensive catalog of theme songs. She performed Yakusoku da yo for the series No Need for Tenchi! in 1989. For the All Purpose Cultural Cat Girl Nuku Nuku franchise, she recorded the songs Haruneko fushigi tsukiyo -oshiete Happiness- (1992), Yume Hurry Up (1993), Fine Colorday (1998), and A House Cat (1998). Her single Over Soul, released in 2001, was used as an opening theme for Shaman King, followed by the single Brave Heart as an insert song for the same series. The single Northern Lights followed in 2002 for Shaman King as well. Additional theme song credits include Successful Mission for Saber Marionette J (1996), ~infinity~ for Lost Universe (1998), Proof of Myself for Saber Marionette J to X (1998), Sakura Saku for Love Hina (2000), A Happy Life for Gakuen Utopia Manabi Straight! (2007), and the singles Shuuketsu no sono he (2009) and Shuuketsu no sadame (2010) which are connected to Neon Genesis Evangelion. The single Soul Salvation was released in 2021.

In addition to performing, Hayashibara has been active as a lyricist, often writing under the name MEGUMI. She wrote the lyrics for Don't be Discouraged, as well as for other Slayers songs such as Just Be Conscious, Reflection, and songs from later seasons like Plenty of Grit and Front Breaking. Her musical style is predominantly J-pop, closely tied to the anime genre for which she has become a defining artist. Her industry significance is reflected in the commercial success of her recordings, with multiple singles and albums consistently placing in the top ten of the Oricon charts throughout the 1990s and 2000s.