Just Mustard is an experimental rock band from Ireland, formed in Dundalk, County Louth, in 2015. The group fronted by singer Katie Ball initially gained traction with their debut album Wednesday, released in 2018 through Pizza Pizza Records. Self-produced and recorded at their home studio in Dundalk and Start Together Studios in Belfast, the album was nominated for the Choice Music Prize in 2018. In 2020, Just Mustard signed to Brooklyn-based label Partisan Records, which released their sophomore album Heart Under in May 2022. The album peaked at number 17 on the Irish albums chart and received critical acclaim. Notable singles include "Seven" (2019) and "I Am You" (2021). In 2025, the band released their third album We Were Just Here.