Mass of the Fermenting Dregs (マス オブ ザ ファーメンティング ドレッグス, Masu obu za Fāmentingu Doreggusu) (capitalized in its stylization) is a post-hardcore/shoegaze trio formed in Kobe, Japan, in 2002.

They are known for a tightly arranged, guitar-driven style, melodic pop vocals and a high-energy stage presence at their live events.

Mass of the Fermenting Dregs was formed in 2002 in Kobe, Hyogo Prefecture, with the original all-female lineup of Natsuko Miyamoto, Chiemi Ishimoto and Reiko Gotoh.

Their breakthrough came at the 2007 "Road to Tarbox Audition" competition held by EMI Japan, which put the band in contact with noted American record producer Dave Fridmann (The Flaming Lips, OK Go) of Tarbox Road Studios.

In 2010, support drummer Isao Yoshino became an official member of the band, prior to the release of their major label debut album.

A song titled "たんたんたん" (tantantan) was made available for download through a direct link placed within the page containing the departing letter to the fans on the official M.o.F.D.

[1] The band's sound is often compared to that of other influential Japanese post-hardcore acts, notably NUMBER GIRL (ナンバー・ガール).