Freestyle rap (also known as battle rap, battle rapping or battle rhyming) commonly refers to rap lyrics which are improvised through an a cappella or with instrumental beats, i.e. performed with no previously composed lyrics, or "off the top of the head". It is similar to other improvisational music such as jazz - Myka 9 of Freestyle Fellowship describes it as being "like a jazz solo" where there is a lead saxophonist acting as the improviser and the rest of the band providing the beat. Rap battles are sometimes improvised in this way. It is similar in both form and function to the ancient practice of flyting.

Originally, in Old school hip hop of the 1980s, the term ‘freestyle’ referred to a pre-written rap verse that was not on any particular subject matter, but rather was written for the purpose of demonstrating skill. The term is still occasionally used in this way, though since the 1990s, the majority of today’s artists use it to mean improvised rapping.

Battling is generally believed to have originated in the East Coast hip hop scene in the late 1970s.^{[citation needed]} One of the earliest and most famous battles was in December 1981 (evidenced by BB's DJ asking if the crowd is ready for '82) when Kool Moe Dee challenged Busy Bee Starski - Busy Bee Starski's defeat by the more complex raps of Kool Moe Dee meant that "no longer was an MC just a crowd-pleasing comedian with a slick tongue; he was a commentator and a storyteller", which KRS-One also credits as creating a shift in rapping in the documentary Beef.