Big Walter Horton or Walter "Shakey" Horton (April 6, 1917– December 8, 1981) was an American blues harmonica player.

Born Walter Horton in Horn Lake, Mississippi, he was playing a harmonica by the time he was five years old. In his early teens, he lived in Memphis, Tennessee and claimed that his earliest recordings were done there in the late 1920s with the Memphis Jug Band, although there is no documentation, and many have since disputed this claim. (He also claimed to have taught some harmonica to Little Walter and the original Sonny Boy Williamson, although these claims are unsubstantiated, and in the case of the older Williamson, somewhat suspect.) As with many of his peers, he spent much of his career existing on a meager income and living with constant discrimination in a segregated America. In the 1930s he played with various blues performers across the Mississippi delta region. It's generally accepted that his first recordings were made in Memphis, backing guitarist Little Buddy Doyle on recordings for the Okeh and Vocalion Records labels, in 1939. These recordings were in the acoustic duo format popularized by Sleepy John Estes with his harmonicist Hammie Nixon, among others. On these recordings, Walter's style is not yet fully realized, but there are clear hints of what is to come. He eventually stopped playing the harp for a living due to poor health, and worked mainly outside of music in the 1940s. By the early 1950s, he was playing music again, and was among the first to record for Sam Phillips at Sun Records in Memphis, who would later record rock and roll superstars Elvis Presley, Carl Perkins, and country giant Johnny Cash. The early Big Walter recordings from Sun include performances from a young Phineas Newborn, Jr. on piano, who later gained fame as a jazz pianist.

During the early 1950s he first appeared on the Chicago Blues scene, where he frequently played with fellow Memphis and Delta musicians who had also moved north, including guitarists Eddie Taylor and Johnny Shines. When Junior Wells left the Muddy Waters band at the end of 1952, Horton replaced him in Muddy's band long enough to play on one session with Muddy in January 1953. Big Walter's style had by then fully matured, and he was playing in the heavily amplified style that became one of the trademarks of the Chicago Blues sound. His harmonica playing is characterized by a deep, rich tone, and precise articulation, using the full register of the harp and utilizing the higher notes of the harp with great dexterity. His tone was consistently deeper or 'heavier' than Little Walter's, but with phrasing that was more in keeping with the Memphis traditions, and less adventurous and improvisational than the jazzier explorations employed by his chief harmonica rival Little Walter. He also made great use of techniques such as tongue-blocking. Many blues harmonica aficionados consider Horton's solo on Jimmy Rogers' 1956 Chess recording "Walking By Myself" to be his greatest moment, and a high point of post-war Chicago Blues.

Also known as "Mumbles", and "Shakey" because of his head motion while playing the harmonica, Horton was active on the Chicago Blues scene during the 1960s as blues music gained popularity with white audiences. From the early 1960s onward, he recorded and appeared frequently as a sideman with Eddie Taylor, Johnny Shines, Johnny Young, Sunnyland Slim, Willie Dixon and many others. He toured extensively, usually as a backing musician, and in the 1970s he performed at blues and folk festivals in the U.S. and Europe, frequently with Willie Dixon's Chicago Blues All-Stars. He has also appeared as a guest on recordings by blues and rock stars such as Fleetwood Mac and Johnny Winter. In October 1968, while tourning the UK, he cut the album Southern Comfort with the former Savoy Brown Blues Band and future Mighty Baby guitarist Martin Stone. In the late 1970s he toured the country with Homesick James Williamson, Richard Molina, Bradley Pierce Smith and Paul Nebenzahl, and appeared on National Public Radio broadcasts. His musical output was somewhat inconsistent over the course of his career, unpredictably wavering between brilliant and workmanlike, and much of his best work was done as a sideman. Some of the best compilations of his own work are Mouth-Harp Maestro and Fine Cuts. Also notable is the low-key but excellent Big Walter Horton and Carey Bell album released by Alligator Records in 1972.

A quiet, unassuming man, Horton is remembered as one of the most gifted harmonica players in the history of blues music. He died in Chicago in 1981 at the age of 64, and was buried in the Restvale Cemetery in Alsip, Illinois.