The award was made to recognise Haymarket Business Media's outstanding performance across all its digital publishing activities, including GPonline.com.
The judging panel recognised that the business publisher was 'doing great things with an effective, long-term engagement strategy'.
Matthew Gerry, Haymarket Business Media's digital strategy director, said: "An AOP award is one of the top prizes in UK media so we are delighted the judges have recognised Haymarket.
'This award is a reflection of the creative endeavour of our editorial and commercial teams, including GPonline.com.'
Kevin Costello, chief executive of Haymarket Media Group, said: 'I’m thrilled that the effort, energy and commitment of all our Business Media digital teams has been recognised by the AOP.
'We have invested significantly in the development of our digital platforms and are now enjoying returns and growth.'
Haymarket Business Media also publishes sites such as Brand Republic, Campaign, Horticultural Week and Third Sector.
The awards evening was attended by 1,000 people at the Roundhouse in Camden, London.