Mustard Plug is an American ska punk band from Grand Rapids, Michigan, consisting of Dave Kirchgessner (vocals), Brandon Jenison (trumpet), Jim Hofer (trombone), Nate Cohn (drums), Colin Clive (guitar/vocals), Mark Petz (tenor saxophone) and Greg Witulski (bass).

Formed in 1991, the band has regularly toured throughout the United States, Europe, Japan, and South America. They have toured with the Warped Tour twice, and participated in the Ska Against Racism Tour. As of 2024^[update], the band has released eight studio albums and continues to tour actively.

Explaining the band's goal, Jim Hofer said, "We may have some messages in our music, but essentially we just do this because we love it and we want people to lighten up and have fun."

The band formed in 1991 after Colin and Dave both attended a Special Beat show. The band's original members were Dave Kirchgessner, Mike McKendrick, Colin Clive, and Anthony Vilchez. There was virtually no ska scene in Grand Rapids at the time, so Mustard Plug was able to develop a unique sound and draw a large following.

Brandon Jenison stated in an interview that their band name originated when "a guy in the early stages of the band was making a sandwich and that crusty stuff that forms on the mustard bottle when you put it in the fridge without wiping it off first gave him an interesting idea for a name."

In 2002, the band released Yellow #5, and supported the album for years on tour. In 2005, they released the "greatest hits" album Masterpieces: 1991–2002.

Mustard Plug was on the label Hopeless Records for many years, but had a period of free agency until their signing with Bad Time Records.

The band celebrated their 20th anniversary in 2011 with a national tour.