Rockabilly is one of the earliest styles of rock and roll music, dating to the early 1950s. The term rockabilly is a portmanteau of rock (from rock 'n' roll) and hillbilly, the latter a reference to the country music (often called hillbilly music in the 1940s and 1950s) that contributed strongly to the style's development. Other important influences on rockabilly include western swing, boogie woogie, and rhythm and blues. While there are notable exceptions, its origins lie primarily in the Southern United States.

There was a close relationship between the blues and country music from the very earliest country recordings in the 1920s. The first nationwide country hit was "Wreck of the Old '97", backed with "Lonesome Road Blues", which also became very popular. Jimmie Rodgers, the "first true country star", was known as the "Blue Yodeler", and most of his songs used blues-based chord progressions, although with very different instrumentation and sound from the recordings of his black contemporaries like Blind Lemon Jefferson and Bessie Smith.

During the 1930s and 1940s, two new sounds emerged. Bob Wills and his Texas Playboys were the leading proponents of Western Swing, which combined country singing and steel guitar with big band jazz influences and horn sections; Wills's music found massive popularity. Recordings of Wills's from the mid 40s to the early 50s include "two beat jazz" rhythms, "jazz choruses", and guitar work that preceded early rockabilly recordings. Wills is quoted as saying "Rock and Roll? Why, man, that's the same kind of music we've been playin' since 1928!... But it's just basic rhythm and has gone by a lot of different names in my time. It's the same, whether you just follow a drum beat like in Africa or surround it with a lot of instruments. The rhythm's what's important."
After blues artists like Meade Lux Lewis and Pete Johnson launched a nationwide boogie craze starting in 1938, country artists like Moon Mullican, the Delmore Brothers, Tennessee Ernie Ford, Speedy West, Jimmy Bryant, and the Maddox Brothers and Rose began recording what was known as "Hillbilly Boogie", which consisted of "hillbilly" vocals and instrumentation with a boogie bass line.

The Maddox Brothers and Rose were at "the leading edge of rockabilly with the slapped bass that Fred Maddox had developed". Maddox said, "You've got to have somethin' they can tap their foot, or dance to, or to make 'em feel it." After World War II the band shifted into higher gear leaning more toward a whimsical honky-tonk feel, with a heavy, manic bottom end - the slap bass of Fred Maddox. "They played hillbilly music but it sounded real hot. They played real loud for that time, too..."The Maddoxes were also known for their lively "antics and stuff." "We always put on a show... I mean it just wasn't us up there pickin' and singing. There was something going on all the time." "...the demonstrative Maddoxes, helped release white bodies from traditional motions of decorum... more and more younger white artists began to behave on stage like the lively Maddoxes." Others believe that they were not only at the leading edge, but were one of the first Rockabilly groups, if not the first.

Zeb Turner's February 1953 recording of "Jersey Rock" with its mix of musical styles, lyrics about music and dancing, and guitar solo, is another example of the mixing of musical genres in the first half of the 1950s.
Bill Monroe is known as the Father of Bluegrass, a specific style of country music. Many of his songs were in blues form, while others took the form of folk ballads, parlor songs, or waltzes. Bluegrass was a staple of country music in the early 1950s, and is often mentioned as an influence in the development of rockabilly.
The Honky Tonk sound, which "tended to focus on working-class life, with frequently tragic themes of lost love, adultery, loneliness, alcoholism, and self-pity", also included songs of energetic, uptempo Hillbilly Boogie. Some of the better known musicians who recorded and performed these songs are: the Delmore Brothers, the Maddox Brothers and Rose, Merle Travis, Hank Williams, Hank Snow, and Tennessee Ernie Ford.

Curtis Gordon's 1953 "Rompin' and Stompin' ", an uptempo hillbilly-boogie included the lyrics, "Way down south where I was born, They rocked all night 'til early morn', They start rockin', They start rockin' an rollin'."