The financial group has grown from a series of acquisitions and mergers to become the fifth largest insurer in the world.
The review aims to move its planning and buying operations in 28 countries into one agency or network. It will include the media requirements for the Aviva-owned motoring company RAC.
At present, Omnicom handles Aviva's £50m media business in the UK, the company's biggest advertising market, while Aegis handle it in Ireland and WPP controls its French business.
All incumbent networks have been briefed in the last 24 hours and will receive Requests for Information (RFIs) next week.
The pitch process is being led from Aviva's London headquarters by marketing operations director Jan Gooding.
She joined Aviva from British Gas last year, ahead of the company's rebrand in the UK.
According to figures from The Nielsen Company, Aviva spent £47m on media in the 12 months to the 30 June, including £27m on TV ads, £10.5m on press and £2.5m on outdoor.
In addition, the financial group spent an additional £13.5m on direct mail and mail drops not included in the review.
A spokesman for Aviva said: "We are undertaking a review of all our media planning and buying agencies with a view to consolidating the business into one agency or network.
"The move forms part of a more strategic approach following the transformation of the business which saw Norwich Union rebrand as Aviva from 1 June."
There are no plans to review the group’s creative requirements, the bulk of which is handled by Abbott Mead Vickers BBDO in a number of markets, including the UK.However, a review of Aviva’s direct marketing business, worth £13m in the UK alone, is expected to take place.
OMD has held the UK part of the business since December 2005, prior to which the Norwich Union account was handled by Brand Connection and the RAC business was serviced by Vizeum.
This change is part of the transformation set out by Andrew Moss, chief executive, in October 2007 in the "One Aviva, twice the value" vision, which aims to maximise the company’s full potential as a global group.
Over the last few years, Aviva has brought together more than 40 different trading names around the world.
The global rebrand will be completed at the start of 2010, when operations in Ireland and Poland, currently known as Hybernian and Commerical Union Poland respectively, will change to the Aviva name.
Aviva became the new name for the former CGNU in July 2002. CGNU was formed in 2000 by the merger of Norwich Union and CGU, itself the result of the merger of Commercial Union and General Accident in 1998.