During the 1970s, one of the most dominating forces within the field of popular music was a group from Sweden called ABBA, a musical entity consisting of two couples, who became by far the most successful act of that decade, even one of the biggest phenomenons of the whole century. As far as the world knew, ABBA's story started in April, 1974 when they won the Eurovision Song Contest with a tune called "Waterloo", but by that time the group had existed for two years and the individual members were virtual show business veterans in their native Sweden. It all began in June, 1966, when Bjorn Ulvaeus met Benny Andersson for the first time. Bjorn was a member of The Hootenanny Singers, a popular Folk music group, while Benny was a member of The Hep Stars, Sweden's number one Pop band at the time. In the Summer of 1966, the two groups were touring Sweden's popular open-air Folkpark circuit when they happened to meet up at a crossroads. The Hootenanny Singers were planning a party that night and invited The Hep Stars to come along. Bjorn and Benny soon found that they had a lot in common, and when they met at another party later that Summer, they decided that they should try to write something together. With the help of Bjorn's father, they transported all the instruments and amplifiers to his office in the middle of the night. The result was a song called "Isn't It Easy To Say", which was later recorded by The Hep Stars, and the first seeds had been sown for what eventually would blossom into ABBA.

By 1969, the popularity of the two groups had begun to wane somewhat, and after their respective Summer tours of that year, The Hootennany Singers became more or less a recording act doing the occasional live performance, while Benny chose to leave The Hep Stars altogether. The two friends continued to write and record songs, encouraged by record company owner and publisher Stig Anderson who was to become ABBA's manager. Stig had great belief in the songwriting and producing talents of Bjorn and Benny, assuring them that they would achieve worldwide success sooner or later.

The second Bjorn and Benny single was a song called "Hej gamle man!" ("Hey Old Man!") which featured the backing vocals of their respective fiancees, Agnetha Fältskog and Anni-Frid "Frida" Lyngstad, the first time the four future ABBA members appeared on the same record. Frida, who had been a recording artist since the Autumn of 1967, had met Benny when she appeared with a cabaret act in the town of Malmo in the South of Sweden in March 1969. The Hep Stars had an engagement at another venue in the same town. Agnetha, a successful solo singer since her breakthrough in early 1968, had met and fallen in love with Bjorn in May 1969 when the two of them appeared in the same TV special. It was as the cabaret act, Festfolk, having the double meaning "engaged couples" and "party people", that the foursome first introduced themselves to the public in November 1970. This first attempt was ultimately not very successful, and all thoughts on a permanent group where shelved for the time being. Meanwhile, they continued to appear on each other's records, and working together in different constellations. In July 1971, Bjorn and Agnetha got married, and in the Autumn of that year Bjorn and Benny started working as house producers at Stig Anderson's record company Polar.

In the Spring of 1972, it was decided to try the foursome concept again, and the first true ABBA single, "People Need Love", was recorded. Released under the somewhat clumsy name "Bjorn & Benny, Agnetha & Anni-Frid", it became a Top Twenty hit in Sweden. On the back of that success, the two couples started to record a whole album together in the Autumn of 1972, although they were far from sure if there was any long-term future in the group. In February 1973, they took part in the Swedish heats for the Eurovision Song Contest with "Ring Ring", a song composed by Bjorn, Benny and Stig. At the time of the contest, Agnetha was highly pregnant with Bjorn's and her first child, daughter Linda. The group only finished third that year, but the Swedish and English-language singles and the album of the same name were by far the most popular of the Swedish contestants, and they soon found themselves at the top three places of the Swedish combined singles and albums chart. It was only with this final confirmation of their popularity that the four decided to put their respective solo careers on the back burner and concentrate on the group.

Everyone realized that the name Bjorn & Benny, Agnetha & Frida (as Anni-Frid now was called on their records) was far too unpractical. For the sake of convenience, Stig Anderson had come to refer to them as ABBA, an acronym of their Christian names, and when a "think of a name for Bjorn & Benny, Agnetha & Frida" competition held in a newspaper reached the same conclusion, the decision was sealed. The only problem was that there already existed a Swedish canned fish company of that name, but when Stig asked them if they would mind lending their name to a popular music group, they fortunately did not object.

In April, 1974, the group again entered the Eurovision Song Contest, which that year was held in Brighton. They performed "Waterloo", a song written by Benny, Bjorn & Stig, and walked away as winners of the Swedish Eurovision heat. "Waterloo" became the first of the group's nine UK number one singles, and launched ABBA as the first internationally successful Pop/Rock superstar act who sang in a language other than their native tongue. The "Waterloo" single also topped charts around the world, as well as making the US Top 10, and while the group reached the charts on both sides of the Atlantic with follow-up singles, for over a year they seemed unable to overcome the apparent stigma which has afflicted non-British Eurovision winners. However, in the Autumn of 1975, "SOS" returned them to the UK Top 10 and US Top 20. During this period of uncertainty, their fame in non-English speaking markets (Scandinavia, Germany, Benelux, Spain, etc.) was fast increasing, and at the start of 1976, they returned to the top of the UK singles chart with "Mamma Mia", which also topped the charts in Germany. "Money, Money, Money", released in 1976 (with "Crazy World" as the B-side), reached the #3 spot on the UK charts.

Their next dozen consecutive singles released up to the end of 1979 reached Top 5 on the UK chart, and included five more UK number one hits; "Fernando" (which topped the charts in Holland and Australia), "Dancing Queen" (also their only US Number One), "Knowing Me, Knowing You" (another German number one), "The Name Of The Game" and "Take A Chance On Me". Between 1976 and 1979, five consecutive ABBA albums topped the UK chart. During this period, ABBA were at number one on the UK album chart for 36 weeks of a possible 192. The only group to have spent more weeks at the top of the UK album chart by the end of 1991 was The Beatles.

In 1977, just as "Knowing Me, Knowing You" was released to become their fourth number one record in fifteen months, ABBA embarked on their first tour of Britain, during which they filled the Royal Albert Hall. 1977 was also the year when the group starred in a feature film made in Australia, where they were incredibly popular. ABBA - The Movie, jointly produced by Stig Anderson and Reg Grundy, an Australian who was later responsible for the incredibly popular Neighbours TV series, was released also in 1978 to immense box office success, but little critical acclaim. 1978 also saw Benny and Frida, who lived together for several years, finally getting married, so that for the first time, ABBA was composed of two husband and wife teams. This situation lasted less than three months, as Agnetha and Bjorn separated.

The first of ABBA's 1979 albums, "Voulez-Vous", was seen as a departure from previous work, as it was a much more personal collection in lyrical terms, with several songs about the tribulations of romance from which the group members were suffering. "I Have A Dream", ABBA's final UK single of a decade which they had dominated, topped the Dutch charts, and was different again, a sing-a-long item which was specially recorded live at Wembley Arena with a large choir of children, at the last concert of what would sadly turn out to be ABBA's final world tour. However, it wasn't all over, not by a long shot. 1980 found Benny and Bjorn working on songs for the group's seventh original album, "Super Trouper", which was eventually released at the end of the year, when of course, it instantly topped the UK album chart, a position echoed in the singles chart by the title track, which also outsold everything in Germany and Holland. The album also included another number one single, "The Winner Takes All", a reflective song about the end of a romance which mirrored the emotional situation of each member of the group. In early 1981, Benny and Anni-Frid became another divorce statistic, adding poignancy to Benny and Bjorn's songs. Echoing Agnetha's and Bjorn's statement, Benny and Frida maintained that their marital split did not affect their work with ABBA, and the group soon started recording again. However, with relationships between the couples inevitably strained, Bjorn had remarried, as would Benny before the end of the year. A concert tour was out of the question, although the quartet reconvened for what turned out to be their final original album, "The Visitors", which included another UK Top 3 single of that era, "One Of Us". A few smaller hit singles extracted from the album kept ABBA's name in both the chart and the public eye, but by this time each of the group members was considering future projects outside the ABBA umbrella.

Anni-Frid and Agnetha embarked on solo careers with some success, but the appeal of their records was simply less attractive to record buyers than had been the case with ABBA's output between 1974 and 1982. The release of a compilation double album, "The Singles - The First Ten Years", which predictably topped the UK album chart, perhaps tended to deflect attention away from solo albums by Frida (produced by Phil Collins), or Agnetha. As songwriters, Benny and Bjorn were obviously better placed to prolong their success, and their most notable achievement during the 1980s was probably the musical Chess, which they co-wrote with famed English lyricist Tim Rice. Based on an actual confrontation in Iceland between American and Russian grand masters of the board game, it included several international hit singles and spawned a big selling album released in 1984.

After a few years of Pop music fans being distracted by new groups and new sounds, public interest in the Swedish foursome reached new heights in the 1990s. The compilation album "ABBA Gold", released in 1992, topped the charts the world over, becoming the group's biggest seller ever. On February 2nd, 2000, ABBA turned down an offer worth $1 billion to get together again after seventeen years. The offer came from an American-British consortium which wanted ABBA to reunite for a hundred concerts to cash in on the current international revival of the catchy songs that brought the group fame and fortune. "It is a hell of a lot of money to say no to, but we decided it wasn't for us", Benny Andersson told the Swedish tabloid Aftonbladet. "We have never made a comeback. Almost everyone else has. I think there is a message in that".

In September, 2012, it was announced that a museum devoted to ABBA would open in 2013 in Stockholm. In early October, Agnetha Faltskog revealed that she was preparing a new album after a break of more than eight years. In November, 2013, Faltskog said that members of the band were planning to mark the 2014 anniversary of the single "Waterloo", which propelled the group to success at the Eurovision Song Contest in 1974. However, she played down suggestions they would stage a formal reunion by insisting they are too old, adding, "I cannot imagine that we would go on stage with crutches." In an interview in December, 2014, Bjorn Ulvaeus said that although the band never officially broke up, they won't ever tour again. "We took a break in '82 and it was meant to be a break. It's still a break and will remain so. You'll never see us on stage again." The four of them did appear together in public on January 20th, 2016 when Bjorn opened a theater-restaurant in Stockholm based on and named after "Mamma Mia". Ulvaeus said that he invited the three of his former band mates to the opening but did not know until that night if they would come. The four reportedly mixed with the 130 guests after posing for group pictures.

On June 5th, 2016, the seemingly impossible happened when the four members of ABBA performed alongside one another for the first time since 1982 at a private gala to mark fifty years since songwriting duo Bjorn Ulvaeus and Benny Andersson met for the first time in Stockholm. The impromptu performance reportedly began when Agnetha Faltskog and Anni-Frid Lyngstad recited their 1980 hit "Me and I" as a tribute to Andersson and Ulvaeus, before the two others joined in and made the reunion official. Lyngstad later said, "It was absolutely amazing. A lot of emotions." In late October, 2016, the quartet was back in the news again when they announced that they would reunite for a project with music mogul Simon Fuller. The new venture would involve virtual reality and artificial intelligence to produce what they described as a "new entertainment experience." Details of that collaboration were officially announced in September, 2017 when Benny Andersson revealed that ABBA would be heading back to the stage for their first tour in three decades, to perform as holograms. The digital ABBA stars will appear with a live band, featuring vocals taken from audio recordings of their 1977 Australian tour. Andersson told Australia's Herald Sun, "It'll be like you're in 1977, with a live band, live backing vocals, a great set design with lights and sound, everything will be like a live concert."

As a testament to their popularity, ABBA were second only to Volvo as Sweden's biggest export earners for several years, and remain revered and legendary as one of the most accomplished Pop / Rock groups ever.