Albert J. Jackson Jr. (November 27, 1935 – October 1, 1975) was an American drummer, producer, and songwriter. He was a founding member of Booker T. & the M.G.'s, a group of session musicians who worked for Stax Records and produced their own instrumentals. Jackson was affectionately dubbed "The Human Timekeeper" for his drumming ability. He was posthumously inducted into the Memphis Music Hall of Fame in 2015, and the Rock and Roll Hall of Fame as a member of Booker T. & the M.G.'s in 1992.

Jackson's father, Al Jackson Sr., led a jazz/swing dance band in Memphis, Tennessee. The young Jackson started drumming at an early age and began playing on stage with his father's band in 1940, at the age of five. He later played in producer and trumpeter Willie Mitchell's band and at the same time was holding down a chair in the popular Ben Branch Band.

In an interview with Drum! magazine, Mitchell recalled,

Al Junior was about 14 years old then. I said to his father, 'Hey, let's use your son!' He said, 'Oh, man, he can't play this stuff!' But he did make the gig. He set up his kit – a cymbal, a snare drum, and a bass drum – and I kicked the thing off. And, man, that thing went off at 20 tempos!

But that was around 7:00 o'clock. And by the time Al Senior came in an hour later, at 8:00 o'clock, Al Jackson Jr. was swinging that damn band like a pro.

Future bandmates Steve Cropper and Donald "Duck" Dunn first heard Jackson playing in Mitchell's band at the Flamingo Room, and the all-white Manhattan Club. Mitchell had also hired Booker T. Jones for his band. It was Jones who suggested Jackson be brought to Stax. He said, "You guys need to know about Al." Dunn said that Jackson almost caused his wife to divorce him, because after finishing his own gig at one o'clock, he would stop by a club to hear Jackson and would get home at four or five in the morning; "He was that good!" said Dunn. At first, Jackson was reluctant to join Stax. He felt he could make more money playing live than doing session work. He wanted a guaranteed regular salary to come over to Stax (although he continued to play on sessions produced by Mitchell for Hi Records). And so he became the first Stax session musician to be on a weekly salary.

At Stax, Jackson formed the M.G.'s with Booker T. Jones, Steve Cropper and Lewie Steinberg (later to be replaced by Duck Dunn). During his tenure at Stax, he became one of the most influential drummers in the history of recorded music, providing an instantly recognizable backbeat behind the label's artists, including Rufus Thomas, Carla Thomas, Eddie Floyd, Sam & Dave, Otis Redding and blues guitarist Albert King (whose work Jackson also produced).

In the 1970s, he co-wrote and played on several hits by Al Green, including "Let's Stay Together" and "I'm Still in Love with You", at Hi, and he was also a session drummer for many artists, such as Elvis Presley, Bill Withers, Wilson Pickett, Leon Russell, Jerry Lee Lewis, Eric Clapton, Jean Knight, Aretha Franklin, Major Lance, Ann Peebles, Rod Stewart, Shirley Brown, Donny Hathaway and Herbie Mann.