The International Federation of the Phonographic Industry (IFPI) awarded the singer its global artist of the year prize in recognition of her "simply phenomenal" success.
Adele's achievement is particularly notable as her third album 25 was not released until late November.
It went on to become the fastest selling album in British history.
It sold more than 800,000 copies in its first week and with the album kept off streaming sites, its chart success was entirely made up of physical and download sales.
The record's lead single, Hello, also scored considerable international chart success - becoming the first single to be downloaded more than one million times in the US.
The second biggest selling artist of 2015 was Ed Sheeran - despite him not releasing a studio album during the course of the year.
He kept a high profile by winning songwriter of the year at the Ivor Novello Awards and by playing a world tour that included three sold-out nights at London's Wembley Stadium.
Sheeran and Adele are two of five British acts to feature in the IFPI's top 10 alongside Sam Smith, One Direction and Coldplay.
Taylor Swift, who won the award in 2014, fell to number three. She also did not release an album in 2015 but did complete an 85-date tour, the highest-grossing of the year.
The IFPI says its top 10 chart is the only music industry ranking to accurately capture the worldwide popularity of artists across physical formats, downloads and streams.
Previous recipients of the top prize include Swift and One Direction.