"3 O'Clock Blues" or "Three O'Clock Blues" is a slow twelve-bar blues recorded by Lowell Fulson in 1946. When it was released in 1948, it became Fulson's first hit. When B.B. King recorded the song in 1952, it became his first hit as well as "one of the top-selling R&B records of 1952".

"3 O'Clock Blues" effectively launched King's career and remained a part of his concert repertoire throughout his life. The song was included on his first album, Singin' the Blues and since has appeared on several King albums, including a remake in 2000 with Eric Clapton for the Riding with the King album.

Lowell Fulson recorded "Three O'Clock Blues" during his first recording session for Oakland, California-based record producer Bob Geddins in 1946. Fulson, who sang and played guitar, was accompanied by his brother Martin on second guitar. The duo produced several country blues-style songs after World War II.

According to music historian Ted Gioia, the song lyrics start out "as an insomniac's lament, but end up with a weepy farewell more suited to a suicide note":

Well now it's three o'clock in the morning, and I can't even close my eyes ...
Goodbye everybody, I believe this is the end

By the time of the record's release two years later in 1948, Fulson's style had already evolved into a West Coast blues style typified by his hit recordings for Downbeat and Swing Time, such as "Every Day I Have the Blues" and "Blue Shadows". Nonetheless, "Three O'Clock Blues", became a hit and reached number six in the R&B chart.

B.B. King recorded "3 O'Clock Blues" for RPM Records around September 1951. The recording took place at an improvised studio in a room at the Memphis YMCA and the resulting audio quality was lower than recordings by Sam Phillips, who had recorded King's previous singles. Nonetheless, writer Colin Escott notes that the song "clicked where the others hadn't [perhaps due to] the new found drama and urgency in B.B.'s singing [and] the interplay between his voice and guitar, heard for the first time on record". The mingling of these two elements was brought to the forefront by the distant, subdued sound of the accompanying musicians.

...
Wikipedia