Cap'n Jazz is an American emo band from Buffalo Grove, Illinois.

Emo is a music genre characterized by emotional, often confessional lyrics. It emerged as a style of hardcore punk and post-hardcore from the mid-1980s Washington, D.C. hardcore scene, where it was known as emotional hardcore or emocore. The bands Rites of Spring and Embrace, among others, pioneered the genre. In the early-to-mid 1990s, emo was adopted and reinvented by alternative rock, indie rock, punk rock, and pop-punk bands, including Sunny Day Real Estate, Jawbreaker, Cap'n Jazz, and Jimmy Eat World. By the mid-1990s, Braid, the Promise Ring, and the Get Up Kids emerged from Midwest emo, and several independent record labels began to specialize in the genre. Meanwhile, screamo, a more aggressive style of emo using screamed vocals, also emerged, pioneered by the San Diego bands Heroin and Antioch Arrow. Screamo achieved mainstream success in the 2000s with bands like Hawthorne Heights, Silverstein, Story of the Year, Thursday, the Used, and Underoath.