Fe3O4: Break is the second extended play by South Korean girl group Nmixx. It was released by JYP Entertainment and Republic Records on January 15, 2024, and contains seven tracks, including the pre-release single "Soñar (Breaker)" and the lead single "Dash".

Nmixx is a South Korean girl group formed by SQU4D, a sub-label of JYP Entertainment. The group is composed of six members: Lily, Haewon, Sullyoon, Bae, Jiwoo, and Kyujin. Originally a seven-piece group, Jinni departed from the lineup on December 9, 2022, for personal reasons. They debuted on February 22, 2022, with the single album Ad Mare.