Mahalia Jackson (/məˈheɪliə/ mə-HAY-lee-ə; born Mahala Jackson; October 26, 1911 – January 27, 1972) was an American gospel singer, widely considered one of the most influential vocalists of the 20th century. With a career spanning 40 years, Jackson was integral to the development and spread of gospel blues in black churches throughout the U.S. During a time when racial segregation was pervasive in American society, she met considerable and unexpected success in a recording career, selling an estimated 22 million records and performing in front of integrated and secular audiences in concert halls around the world, making her one of the best-selling gospel music artists.

The granddaughter of enslaved people, Jackson was born and raised in poverty in New Orleans. She found a home in her church, leading to a lifelong dedication and singular purpose to deliver God's word through song. She moved to Chicago as an adolescent and joined the Johnson Singers, one of the earliest gospel groups. Jackson was heavily influenced by musician-composer Thomas Dorsey and blues singer Bessie Smith, adapting Smith's style to traditional Protestant hymns and contemporary songs. After making an impression in Chicago churches, she was hired to sing at funerals, political rallies, and revivals. For 15 years, she functioned as what she termed a "fish and bread singer", working odd jobs between performances to make a living.

Nationwide recognition came for Jackson in 1947 with the release of "Move On Up a Little Higher", selling two million copies and hitting the number-two spot on Billboard charts, both firsts for gospel music. Jackson's recordings captured the attention of jazz fans in the U.S. and France, and she became the first gospel recording artist to tour Europe. She regularly appeared on television and radio, and performed for many presidents and heads of state, including singing the national anthem at John F. Kennedy's Inaugural Ball in 1961. Motivated by her experiences living and touring in the South and integrating a Chicago neighborhood, she participated in the civil rights movement, singing for fundraisers and at the March on Washington for Jobs and Freedom in 1963. She was a vocal and loyal supporter of Martin Luther King Jr. and a personal friend of his family.

Throughout her career, Jackson faced intense pressure to record secular music, but she turned down high-paying opportunities to concentrate on gospel. Completely self-taught, Jackson had a keen instinct for music, her delivery marked by extensive improvisation with melody and rhythm. She was renowned for her powerful contralto voice, range, an enormous stage presence, and her ability to relate to her audiences, conveying and evoking intense emotion during performances. Passionate and at times frenetic, she wept and demonstrated physical expressions of joy while singing. Her success brought about international interest in gospel music, initiating the "Golden Age of Gospel" making it possible for many soloists and vocal groups to tour and record. Popular music as a whole felt her influence and she is credited with inspiring rhythm and blues, soul, and rock and roll singing styles. A Grammy Lifetime Achievement Award recipient, she won three competitive Grammy Awards and was inducted into the Grammy Hall of Fame, the National Recording Registry, and the Rock & Roll, Gospel, and R&B Halls of Fame, as well as the Hollywood Walk of Fame and Black Music & Entertainment Walk of Fame. She was also named one of NPR's 50 Great Voices, and ranked among Rolling Stone's 200 Greatest Singers of All Time.

Mahalia Jackson was born to Charity Clark and Johnny Jackson, a stevedore and weekend barber. Clark and Jackson were unmarried, a common arrangement among black women in New Orleans at the time. He lived elsewhere, never joining Charity as a parent. Both sets of Mahalia's grandparents were born into slavery, her paternal grandparents on a rice plantation and her maternal grandparents on a cotton plantation in Pointe Coupee Parish about 100 miles (160 km) north of New Orleans. Charity's older sister, Mahala "Duke" Paul, was her daughter's namesake, sharing the spelling without the "I". Duke hosted Charity and their five other sisters and children in her leaky three-room shotgun house on Water Street in New Orleans' Sixteenth Ward. The family called Charity's daughter "Halie"; she counted as the 13th person living in Aunt Duke's house. As Charity's sisters found employment as maids and cooks, they left Duke's, though Charity remained with her daughter, Mahalia's half-brother Peter, and Duke's son Fred. Mahalia was born with bowed legs and infections in both eyes. Her eyes healed quickly but her Aunt Bell treated her legs with grease water massages with little result. For her first few years, Mahalia was nicknamed "Fishhooks" for the curvature of her legs.

The Clarks were devout Baptists attending nearby Plymouth Rock Baptist Church. Sabbath was strictly followed, the entire house shut down on Friday evenings and did not open again until Monday morning. As members of the church, they were expected to attend services, participate in activities there, and follow a code of conduct: no jazz, no card games, and no "high life": drinking or visiting bars or juke joints. Dancing was only allowed in the church when one was moved by the spirit. The adult choir at Plymouth Rock sang traditional Protestant hymns, typically written by Isaac Watts and his contemporaries. Jackson enjoyed the music sung by the congregation more. These songs would be lined out: called out from the pulpit, with the congregation singing it back. They had a stronger rhythm, accentuated with clapping and foot-tapping, which Jackson later said gave her "the bounce" that carried with her decades later. She dutifully joined the children's choir at age four. Next door to Duke's house was a small Pentecostal church that Jackson never attended but stood outside during services and listened raptly. Music here was louder and more exuberant. The congregation included "jubilees" or uptempo spirituals in their singing. Shouting and stomping were regular occurrences, unlike at her own church. Jackson later remembered, "These people had no choir or no organ. They used the drum, the cymbal, the tambourine, and the steel triangle. Everybody in there sang, and they clapped and stomped their feet, and sang with their whole bodies. They had a beat, a rhythm we held on to from slavery days, and their music was so strong and expressive. It used to bring tears to my eyes."

When Jackson was five, her mother became ill and died, the cause unknown. Aunt Duke took in Jackson and her half-brother at another house on Esther Street. Duke was severe and strict, with a notorious temper. Jackson split her time between working, usually scrubbing floors and making moss-filled mattresses and cane chairs, playing along the levees catching fish and crabs and singing with other children, and spending time at Mount Moriah Baptist Church where her grandfather sometimes preached. The full-time minister there gave sermons with a sad "singing tone" that Jackson later said would penetrate to her heart, crediting it with strongly influencing her singing style. Church became a home to Jackson where she found music and safety; she often fled there to escape her aunt's moods. She attended McDonough School 24, but was required to fill in for her various aunts if they were ill, so she rarely attended a full week of school; when she was 10, the family needed her more at home. She dropped out and began taking in laundry.

Jackson worked, and she went to church on Wednesday evenings, Friday nights, and most of the day on Sundays. Already possessing a big voice at age 12, she joined the junior choir. She was surrounded by music in New Orleans, more often blues pouring out of her neighbors' houses, although she was fascinated with second line funeral processions returning from cemeteries when the musicians played brisk jazz. Her older cousin Fred, not as intimidated by Duke, collected records of both kinds. The family had a phonograph and while Aunt Duke was at work, Jackson played records by Bessie Smith, Mamie Smith, and Ma Rainey, singing along while she scrubbed floors. Bessie Smith was Jackson's favorite and the one she most-often mimicked.