Twain was born in Windsor, Ontario, daughter of Clarence Edwards and his wife Sharon (née Morrison). Her parents divorced when she was two, and her mother then moved with Eilleen and her sister Jill to Timmins, Ontario, where she married Jerry Twain, an Ojibwa. He adopted the girls, legally changing their last name to Twain. Because of her connection to her stepfather, in the past, people had presumed Twain's ancestry was Ojibwa, but she stated in an interview that her biological father was part Cree.

One of five children, Eilleen Twain had a hard childhood in Timmins. Her parents earned little, and there was often a shortage of food in the household. She did not confide her situation to school authorities, fearing they might break up the family. In the remote, rugged community, she learned to hunt and to chop wood. Aside from working at an Ontario McDonald's restaurant, Twain began to earn money by singing in local clubs and bars from a very young age to support her family. She was singing in bars at the age of just eight to try to make ends meet, often earning twenty dollars between midnight and two in the morning when the bar had closed, the people remaining. Although she has expressed a dislike for singing in such a smoky atmosphere at such a young age, Shania believes that this was her performing arts school on the road to becoming a successful singer. At one point, while Jerry was at work, her mother drove the rest of the family 425 miles (684 km) to a Toronto homeless shelter for assistance.

At 13, Eilleen Twain, the future "Shania" Twain, was invited to perform on CBC television's Tommy Hunter Show. While attending Timmins High and Vocational School in Timmins, Ontario, she was the singer for a local band called "Longshot" which covered Top 40 music.

In 1984, she sang a duet performance on an album by Canadian musician (and present-day CKTB radio personality) Tim Denis.

When her mother and adoptive father died in a car accident on November 1, 1987, the 22-year-old Twain put her musical career on hold and took care of her family. She and her half-brothers Mark and Darryl, and sister Carrie Ann moved to Huntsville, Ontario, where she supported them by performing at the nearby Deerhurst Resort.

After Twain's siblings moved out on their own, she assembled a demo tape of her songs, and her manager set up a showcase for Twain to present her material to record executives. Twain caught the attention of a few labels, including Mercury Nashville Records, who signed her within a few months. During this time, she changed her name to Shania an Ojibwa word which means "On my way".

Twain's self-titled debut album was released in 1993 to the United States and Canada, gaining her audiences outside of her own country. The album only reached #67 on the US Country Albums Chart; however, it gained many positive reviews by critics. The album yielded two minor hit singles in the United States with "What Made You Say That" and "Dance with the One That Brought You." It was more successful in Europe, where Twain won Country Music Television Europe's "Rising Video Star of the Year" award.

The album failed to sell significant copies initially, although Twain's future success generated enough interest for the album to be certified platinum by the RIAA, denoting sales of over a million.

That same year, Twain sang harmony vocals on Sammy Kershaw's Haunted Heart album.

When rock producer Robert John "Mutt" Lange heard Twain's original songs and singing, he offered to produce her and to write songs with her. After many telephone conversations, they met at Nashville's Fan Fair in June 1993. Twain initially had no idea who he was but expressed a high degree of praise for his demos on the phone. Twain and Lange became very close within just weeks. Lange and Twain either wrote or co-wrote the songs that would form her second studio album, The Woman in Me.

The Woman in Me was released in the Spring of 1995. The album's first single, "Whose Bed Have Your Boots Been Under?" went to #11 on the Billboard Country Chart. This was followed by her first Top 10 and #1 hit single, "Any Man of Mine." Twain had further hits from the album, including the title track which peaked at #14 and three additional #1 hits; "(If You're Not in it for Love) I'm Outta Here!," "You Win My Love," and "No One Needs to Know." As of 2007, it had sold more than 12 million copies. The album was a quick breakthrough, and it came without tour support. Twain's promotion of the album was based largely upon a series of sexy music videos. The Woman in Me won the Grammy Award for Best Country Album as well as the Academy of Country Music award for Album of the Year; the latter group also awarded Twain as Best New Female Vocalist.

In 1997, Twain released her follow-up album, Come on Over. This was the album that would establish her as a successful crossover singer. Slowly, the album started racking up sales. It never hit the top spot, but with the multi-chart hit single "You're Still the One", sales skyrocketed. Other songs like "Don't Be Stupid", "Honey, I'm Home", "Man! I Feel Like a Woman!", "That Don't Impress Me Much" and "From This Moment On" joined the 12 songs that eventually saw release as singles.

The album stayed on the charts for the next two years and Come on Over went on to sell 20 million copies in the United States and over 34 million worldwide, making it the biggest-selling album of all time by a female musician. It is also the eighth biggest-selling album by any type of artist in the US.

Songs from the album won four Grammy Awards over the next two years, including Best Country Song and Best Female Country Performance (for "You're Still the One" and "Man! I Feel Like a Woman!") for Twain. Lange won Grammys for "You're Still the One" and "Come on Over".

Despite the album's record sales it wasn't able to top the Billboard 200, reaching a peak of No. 2. In 1999, the "Come on Over" album was remixed for the European market as a pop album with less country instrumentation and actually gave her the big breakthrough in Europe she and her producer husband were looking for. "Come on over" went to No. 1 on the UK album charts for 11 weeks. It became the biggest selling album of the year in Great Britain and a bestseller in other big European markets as well, selling more than one million copies Germany and nearly 4 million in the UK alone. The songs that had finally drawn European attention to the album were the pop remixed singles "That Don't Impress Me Much", a No.3 in the UK and Top 10 hit in Germany in the summer of 1999, and "Man! I Feel Like a Woman!" which peaked at No. 3 in both the UK and France in autumn of that year. Additionally, the album set the record for the longest ever stay in the Top 20 of The US Billboard 200, remaining in the Top 20 for 99 weeks.

Twain's mainstream pop acceptance was further helped by her appearance in the 1998 first edition of the VH1 Divas concert, where she sang alongside Mariah Carey, Celine Dion, Gloria Estefan and Aretha Franklin and by VH1's 1999 heavily-aired Behind the Music treatment of her, which concentrated on the tragic aspects of her early life as well as her physical attractiveness and Nashville's early resistance to her bared-midriff music videos.

In 1998, Twain launched her first major concert tour, aided by her manager Jon Landau, a veteran of many large-scale tours with Bruce Springsteen. The Come on Over Tour shows were enthusiastically received by audiences around the globe and answered critics who speculated that she could not perform live.

After a two year break, Twain and Lange went back into the studio, along with a management change (QPrime replacing Landau), and recorded her latest CD. Up! was released on November 19, 2002. About a year later, Twain kicked off the Up! Tour in Hamilton, Ontario, Canada on September 25, 2003.

Up! was released as a double album, with three different discs—pop (a red CD), country (a green CD), and Indian film music (a blue CD). For North American markets, the pop disc was paired with the country disc and in international markets, the pop disc was paired with the world music disc. Up! was given four out of five stars by Rolling Stone magazine, and debuted at No. 1 on the Billboard albums chart, selling 874,000 in the first week alone. It charted at the top for five weeks. The success of the album's pop version outside the US was equally amazing when "Up!" reached No.1 in Germany, No.2 in Australia and the Top Five in the UK and France. Especially in Germany it became a real long seller, certified quadruple platinum and stayed in the Top 100 for one and a half years.

The blue, world music disc was remixed with Bollywood-style orchestral and percussion parts recorded in Mumbai, India. The new versions were produced by Simon and Diamond Duggal, brothers from Birmingham, England. They were originally invited to contribute parts to the red, pop version of "I'm Gonna Getcha Good!" which retains the Bollywood influence.

Twain's popularity in UK was reflected by numerous appearances on the long-running music show Top of the Pops, performing singles from Come on Over from 1999. In 2002 an entire special show was dedicated to her on sister show TOTP2, in which Twain herself introduced some past performances of her greatest hits and new singles from Up!

The first single from the album, "I'm Gonna Getcha Good!" became a top 10 country hit in the US, after debuting at an impressive No. 24 after only five days of airplay; but only made the Top 40 on the pop charts. It was a much bigger hit on the other side of the Atlantic, released in a pop version, the single hit the Top Five in the UK and Australia as well as the Top 15 in Germany and France. The follow-up single "Up!" reached the Top 15 in the US country charts but failed to reach the pop Top 40.

The second European single became the mid-tempo song "Ka-Ching!" (which was never released as a single in North America) with lyrics where Twain was criticizing unchecked consumerism. The song eventually became another smash hit in the important European markets, reaching No. 1 in Germany and Austria and other European countries, the UK Top 10 and the Top 15 in France.

The third single from the album would be the most successful in the US. The romantic ballad "Forever and For Always" was released as a single in April 2003 and peaked at No. 4 on the country chart and No. 1 on the Adult Contemporary chart, and made as well the Billboard Top 20. Again success was even bigger on the other side of the Atlantic with "Forever and For Always" again reaching the Top 10 in both, the UK and Germany. Further singles were "She's Not Just a Pretty Face" a country Top 10 hit, while the last US single, "It Only Hurts When I'm Breathing", made the Top 20 on both Country and AC.

Twain's popularity in UK was reflected by numerous appearances on the long-running music show Top of the Pops, performing singles from Come on Over from 1999. In 2002 an entire special show was dedicated to her on sister show TOTP2, in which Twain herself introduced some past performances of her greatest hits and new singles from Up!

Due to the enormous European success of Up! and its first three singles, two more singles were released in the second half of 2003 with up-tempo "Thank You Baby" (No. 11 in the UK, Top 20 in Germany) and just before Christmas the romantic, acoustic ballad "When You Kiss Me", at least a minor hit in both territories. The title track "Up!" also saw a single release in a limited edition of European countries, such as Germany, in early 2004. In January 2008, Up! had sold 5.5 million copies in the U.S. (Certified by the RIAA as 11 times platinum due to the organization's rules regarding double albums, which are counted as two units for certifications).

In 2003, Twain participated in the Dolly Parton tribute album Just Because I'm a Woman, covering Parton's classic "Coat of Many Colors", as a duet with Alison Krauss & Union Station. The cover peaked at No. 57 on the Hot Country Songs charts as an album cut. During the Super Bowl XXXVII halftime show Twain performed two songs, "Man! I Feel Like a Woman!" and "Up!"

In 2004, she released the Greatest Hits album, with three new tracks. As of 2008, it has sold over four million copies in the U.S. The first single, the multi-format duet "Party for Two", made the country top ten with Billy Currington, while the pop version with Sugar Ray lead singer Mark McGrath made top ten in the United Kingdom and Germany. The follow-up singles, "Don't!" and "I Ain't No Quitter" did not fare as well, the former made Top 20 on Adult Contemporary, while the latter did not gain enough airplay to even crack the Country Top 40.

In August 2005, she released the single "Shoes" from the Desperate Housewives soundtrack. It only peaked at No. 29 on the country chart and therefore, a video, which was scheduled to be created, was cancelled.

At the Academy of Country Music Awards in Las Vegas on May 16, 2007, Twain said she was currently writing songs for a new album, and was doing a "lot of soul searching" and "indulging in the writing."

Twain joined Canadian singer Anne Murray on the song "You Needed Me" on Murray's Anne Murray Duets: Friends and Legends album released November 13, 2007 in Canada, and on January 15, 2008 in the US. On November 12 Twain made her first television appearance since her split from now ex-husband Robert "Mutt" Lange, where she appeared as a surprise presenter at the 42nd CMA Awards.