Because of her constantly changing image and tight control over her artistry, Hamasaki's popularity extends across Asia; music and fashion trends she has started have spread to countries such as China, Singapore, and Taiwan. She has appeared in or lent her songs to many advertisements and television commercials. Though she originally supported the exploitation of her popularity for commercial purposes, she later reconsidered and eventually opposed her status as an Avex "product".

Since her 1998 debut with the single "Poker Face",[fn 1] Hamasaki has sold over 50 million records in Japan, ranking her among the best-selling singers in the country. As a female singer, Hamasaki holds several domestic records for her singles, such as the most number-one hits, the highest sales, and the most million-sellers.[fn 2] From 1999 to 2010, Hamasaki had at least one single each year top the charts. Hamasaki is the first female singer to have eight studio albums since her debut to top the Oricon and the first artist to have a number-one album for 11 consecutive years since her debut.

Born in Fukuoka Prefecture, Hamasaki was raised as an only child by her mother and grandmother. Her father had left the family when she was three and never again came into contact with her. Because her mother worked to support the family, Hamasaki was primarily taken care of by her grandmother.

At age seven, Hamasaki began modeling for local institutions, such as banks, to supplement the family's income. She continued this career path by leaving her family at fourteen and moving to Tokyo as a model under SOS, a talent agency. Her modeling career did not last long; SOS eventually deemed her too short for a model and transferred her to Sun Music, a musicians' agency. Under the name of "Ayumi", Hamasaki released a rap EP, Nothing from Nothing, on the Nippon Columbia label in 1995. She was dismissed from the label when the album failed to chart on the Oricon. After this failure, Hamasaki took up acting and starred in B-movies such as Ladys Ladys!! Sōcho Saigo no Hi and television dramas such as Miseinen, which were poorly received by the public. From August 1995 to March 1996, Hamasaki also co-hosted the SoundLink "magazine" Hōkago no Ōsama (放課後の王様?, After-school King) for the Nintendo Satellaview once a week with Shigeru Izumiya. Growing dissatisfied with her job, Hamasaki quit acting and moved in with her mother, who had recently moved to Tokyo.

Hamasaki was initially a good student, earning good grades in junior high school. Eventually however, she lost faith in the curriculum, thinking that the subjects taught were of no use to her. Her grades worsened as she refused to put her mind to her studies. While living in Tokyo, she attempted to further her studies at Horikoshi Gakuen, a high school for the arts, but dropped out in the first year. Because Hamasaki did not attend school or have a job, she spent much of her time shopping at Shibuya boutiques and dancing at Velfarre, an Avex-owned disco club.

At Velfarre, she was introduced to her future producer, Max Matsuura, through a friend. After hearing Hamasaki sing karaoke, Matsuura offered her a recording deal, but Hamasaki suspected ulterior motives and turned the offer down. He persisted and succeeded in recruiting her for the Avex label in the following year. Hamasaki started vocal training, but skipped most of her classes after finding her instructors to be too rigid and the classes dull. When she confessed this to Matsuura, he sent her to New York to train her vocals under another method. During her foreign sojourn, Hamasaki frequently corresponded with Matsuura and impressed him with her style of writing. On her return to Japan, he suggested that she try writing her own lyrics.

Hamasaki made her debut under Avex on April 8, 1998 with the single "Poker Face". It—and the following four singles—were not major hits. Hamasaki's debut album, A Song for ×× (1999), was likewise "unassuming": the tracks, composed by Yasuhiko Hoshino, Akio Togashi (of Da Pump), and Mitsuru Igarashi (of Every Little Thing), were "cautious" pop-rock songs. However, Hamasaki's lyrics, introspective observations about her feelings and experiences that focused on loneliness and individualism, resonated with the Japanese public. The songs gained Hamasaki a growing following, and the release of the album was a success: it topped the Oricon charts for five weeks and sold over a million copies. For her achievements, she earned a Japan Gold Disc Award for "Best New Artist of the Year".

With Ayu-mi-x (March 1999), the first of a series of remix albums, Hamasaki began moving beyond the pop-rock of A Song for ×× and began to incorporate different styles including trance, dance, and orchestra. Hamasaki began to experiment with different musical styles in her singles as well, releasing dance tunes and ballads as well as remixes on the singles which spanned reggae and house. The singles were milestones: Hamasaki earned her first number-one single ("Love: Destiny") and first million-selling single ("A"). Her second studio album, Loveppears (November 1999), not only topped the Oricon charts, it sold nearly 3 million copies. The album also showcased a change in Hamasaki's lyrics. Though the lyrics of Loveppears still dealt with loneliness, many of them were written from a third-person perspective. In support of Loveppears, she held her first tour, Ayumi Hamasaki Concert Tour 2000 A.

From April to June 2000, Hamasaki released the "Trilogy", a series of singles consisting of "Vogue", "Far Away", and "Seasons". The lyrics of these songs focused on hopelessness, a reflection of Hamasaki's disappointment that she had not expressed herself thoroughly in any of her previous lyrics and a sense of shame of her public image. Likewise, many of the songs she wrote for her subsequent studio album, Duty (September 2000), involved feelings of loneliness, chaos, confusion, and the burden of her responsibilities. She described her feelings after the writing as "unnatural" and "nervous". The musical style was darker as well; in contrast with Loveppears, Duty was a rock-influenced album with only one dance song, "Audience". Duty resonated with fans: the "Trilogy" were "hit singles" ("Seasons" was a million-seller), and the album became Hamasaki's best-selling studio album. At the end of 2000, Hamasaki held her first New Year countdown concert at the Yoyogi National Gymnasium.

In 2001, Avex forced Hamasaki to release her first compilation album, A Best, on March 28, putting the album in "competition" with Hikaru Utada's second studio album, Distance. The "competition" between the two singers (which both claimed was merely a creation of their record companies and the media) was supposedly the reason for the success of the albums; both sold over 5 million copies. In support of Duty and A Best, Hamasaki held a tour of Japan's domes, making her one of few "top-drawer" Japanese artists to hold a concert at the Tokyo Dome.