"Sayonara Memories" (さよならメモリーズ, Sayonara Memorīzu, lit. "Goodbye Memories") is a J-pop song by the Japanese band Supercell, written by Ryo. Supercell released it as their second single in February 2010 by Sony Music. A music video was produced for "Sayonara Memories", directed by Takahiro Miki and Taiki Ueda. Lyrically, the song deals with an unrequited love. The single peaked at No. 7 on Japan's weekly Oricon singles chart.

From August 2009 when Supercell released their debut single "Kimi no Shiranai Monogatari", it took Ryo about a month to compose a demo of "Sayonara Memories". Continuing from "Kimi no Shiranai Monogatari", Supercell again employed the vocalist Nagi Yanagi to sing "Sayonara Memories", though officially Yanagi is not a member of Supercell. After becoming a fan of the music composed by Ryo of Supercell, Yanagi contacted him and the two talked about someday collaborating. After being offered to be the singer for "Kimi no Shiranai Monogatari", it was decided that Yanagi would be the singer for Supercell's second album Today Is A Beautiful Day (2011). Previously, Ryo had used the Vocaloid singing synthesizer Hatsune Miku as the vocalist of Supercell's debut album Supercell (2009). In switching to a human singer, Ryo said "that although he loses absolute control over the tone of each and every phrase, working with a singer adds a human element that resonates better with listeners."

"Sayonara Memories" is a J-pop song with instrumentation from electric and bass guitars, drums, piano and violin. According to a book of sheet music published by Yamaha Corporation, it is set in common time, and moves at a quick tempo of 160 beats per minute in the B major key throughout the song. The introduction starts with only piano accompanying Yanagi's vocals, and uses a bridge with added guitar, drums and violin to transition into the first verse. The song continues with the second and third verses, which also serves as the chorus melody, before employing another bridge. The musical structure used in the first three verses is repeated for the next three with different lyrics. After a short seventh verse, a break is employed, followed by the eighth verse. After a short instrumental outro, the song ends with Yanagi singing "Aa, yatto ieta" (ああ　やっと言えた, "Ah I finally said it"), referring to a love confession at the end of the eighth verse.

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