Harold Arlen (February 15, 1905 - April 23, 1986) was an American composer of popular music.

Arlen was born Hyman Arluck, in Buffalo, New York, the child of a Jewish cantor. He learned the piano as a youth and formed a band as a young man. He achieved some local success as a pianist and singer and moved to New York City in his early 20s. As this point, he changed his name to Harold Arlen. He performed on record with the "Buffalodians" orchestra, as well as those of Red Nichols, Henny Hendrickson and Arnold Johnson.

In 1929, Arlen composed his first well-known song: "Get Happy" (with lyrics by Ted Koehler). Throughout the early and mid-1930s, Arlen and Koehler wrote shows for the Cotton Club, a popular Harlem night club, as well as Broadway musicals and Hollywood films. Arlen also continued to perform with some success, most notably on records with Leo Reisman's society dance orchestra.

Arlen's compositions have always been popular with jazz musicians because of his facility at incorporating a blues feeling into conventional American popular songs.

Arlen and Koehler wrote the following hit songs during the early and mid-1930s:

• "Between the Devil and the Deep Blue Sea"
• "I Love A Parade"
• "I've Got the World On A String"
• "I've Got A Right To Sing The Blues"
• "It's Only A Paper Moon"
• "Let's Fall in Love"
• "Ill Wind"
• "Stormy Weather"

In the mid-1930s, Arlen married, and spent increasingly more time in California, writing for movie musicals. It was at this time that he began working with lyricist Yip Harburg. In 1938, the team was hired by Metro-Goldwyn-Mayer to compose songs for The Wizard of Oz. The most famous of these is the song "Somewhere Over the Rainbow".

In the 1940s, Arlen teamed up with lyricist Johnny Mercer, and continued with song hits "Blues In The Night", and Ac-cent-uate The Positive".