Young & RubicamBrands is the umbrella for a collection of marketing services providers led by advertising agency Y&R and digital & direct marketer Wunderman. It has been a wholly owned subsidiary of WPP since 2000, but continues to operate as a largely self-contained group.
DDB's principal founder Bill Bernbach is often considered to be the single most influential figure in post-war advertising. Now a subsidiary of Omnicom, DDB Group also houses a collection of other agencies including CRM network Rapp, branding agency Interbrand and digital specialist Tribal.
One of the original pioneers in global marketing, McCann Erickson was the first ad agency to diversify into other marketing disciplines. The Worldgroup umbrella also contains PR giant Weber Shandwick, and branding specialist Futurebrand as well as healthcare, sales promotion and CRM specialists.
BBDO is arguably the world's most admired creative network, having won more industry awards since 2005 than any other. The main advertising agency is the biggest by revenues in the US, and regional units such as AMV BBDO of the UK and Clemenger BBDO of Australia lead their own local markets.
David Ogilvy created Ogilvy & Mather virtually from scratch in the years after World War II, establishing himself as one of the ad industry's most influential ambassadors. The agency remains a global powerhouse, partnered by satellite networks specialising in healthcare, PR and CRM.
No other advertising agency dominates its home market as comprehensively as Dentsu of Japan, which controls around 30% of all that country's mass media advertising. But although it has also established a strong presence in other Asian territories, the Dentsu brand has no profile in Western markets.
TBWA is the youngest of the three global advertising networks within the Omnicom group, positioned as an alternative agency brand, with a reputation for "disruptive" work. It is best known for its work for keystone clients such as Nissan and especially Apple, for whom it has created a series of iconic marketing campaigns.
The only global advertising network still headquartered in France, Publicis is the biggest brand within the group of the same name, sitting alongside acquired businesses such Leo Burnett and Saatchi. Despite a global presence, the main Publicis Conseil office in Paris remains the network's clear flagship.
Havas Worldwide is the new name for the network previously known as Euro RSCG. It is the dominant network within French marketing group Havas. Despite its Gallic heritage it is now run from New York, and its flagship French office is carving out a separate identity under the name BETC.
FCB readopted its old name in 2014 after several years as Draftfcb. That entity was created in 2006 from the merger of the old Foote Cone & Belding agency with a separate unit within parent Interpublic,direct marketing specialist Draft Worldwide, to create a fully integrated worldwide marketing services giant.
J Walter Thompson - or JWT as it is still widely known - carries the distinction of being the industry's oldest surviving ad agency, tracing its roots back to the mid-19th century. It remains one of the biggest by geographical footprint, with a network stretching across 200 countries.
Now one of three major advertising networks within Publicis Groupe, Leo Burnett pioneered what used to be called the "Chicago school" of advertising, which personalises client brands' core values in the form of a brand mascot: such as Uncle Ben, the Marlboro man or the Jolly Green Giant.
Hakuhodo is Japan's second largest ad agency behind Dentsu, but has an even less widespread international presence, with only a handful of low key subsidiaries outside its domestic market. Its parent company also owns two other major local agencies, Daiko and Yomiko.
SapientNitro joined Publicis Groupe in 2015 following the French company's acquisition of IT consultancy Sapient. It was created from the acquisition of independently owned Nitro. Though it offers a full range of marketing services it is best known for digital.
Digital specialist DigitasLBi is the 5th of six major standalone marketing networks within Publicis, formed from the acquisition and merger of several different digital agencies including Digitas of the US and Europe's LBi.
Grey is the smallest of the four major networks within WPP, although it maintains a substantial international presence in its own right. Creative output has improved dramatically in recent years, but Grey is best-known for diligent account management and long-lasting client relationships.
In its heyday in the 1980s, Saatchi & Saatchi was the world's #1 advertising company, before falling upon hard times a decade later. It's somewhat smaller now, but remains arguably the world's most famous advertising brand, and perhaps the only one recognised by members of the ordinary public.
South Korea's biggest ad agency has established a global marketing network to support its biggest client and part-owner Samsung, proving that "inhouse" agencies can be just as dynamic as traditional third-party ones. Its skillset has been boosted by acquisitions including global network Iris and BMB in the UK.
Mullen Lowe Group was created in 2015 from merger of Interpublic's creatively admired Lowe & Partners network with the Boston-based standalone agency Mullen. It is the latest of several attempts to establish a lasting presence for Lowe in the US, following earlier alliances with Deutsch and Campbell Ewald.
Wieden & Kennedy is a fierce challenger for BBDO's crown as the world's most admired agency. It is already arguably the coolest shop in the business, with an unrivalled reputation for memorable advertising. Not just for cornerstone client Nike, but also for the likes of Old Spice, Chrysler and until recently Heineken.
M&C is the second global advertising agency created by Maurice & Charles Saatchi, after they were ousted from their original business in 1995. In many markets, especially outside North America, it actually overshadows the older network, and also manages its own small collection of diversified specialist subsidiaries.
New York agency McGarryBowen was the most ambitious of Dentsu's Western acquisitions in the 2000s. It has absorbed and rejuvenated the Japanese group's Dentsu-branded outposts in other countries, establishing a significant presence as a global advertising brand in its own right.
Bartle Bogle Hegarty (or BBH) has long ranked as one of the world's most admired creative agencies, with a reputation for stylish, elegant and original advertising. Despite the departure of its founding partners following a full buyout by Publicis Groupe, it has retained its style and strength.
Crispin Porter & Bogusky established a reputation during the 2000s as the hottest creative agency in the US, with a special talent for developing memorable, often brash, occasionally bizarre ideas. The biggest subsidiary of MDC Partners, it has gradually established a global footprint.