"Is You Is Or Is You Ain't My Baby" is a 1944 Louis Jordan song, released as the B-side of a single with "G.I. Jive". "Is You Is or Is You Ain't My Baby" reached #1 on the US folk/country charts. The Louis Jordan recording also peaked at number two for three weeks on the pop chart and peaked at number three on the R&B charts. This was Jordan's second and last country chart No. 1, and the last No. 1 country chart topper for an African American artist until Charley Pride scored his first No.1, All I Have to Offer You (Is Me) on August 9, 1969.
It was co-written by Jordan and Billy Austin. Austin (March 6, 1896 – July 24, 1964) was a songwriter and author, born in Denver, Colorado. The phrase "Is you is or is you ain't" is dialect, apparently first recorded in a 1921 story by Octavus Roy Cohen, a Jewish writer from South Carolina who wrote humorous black dialect fiction. Glenn Miller recorded this song on a radio broadcast from Europe during World War II.