In McDonald's branding history, Heye & Partner created the 2003 “I'm lovin' it” campaign.
Heye & Partner, a German advertising agency, developed the campaign concept that McDonald's launched internationally in 2003. The work introduced the phrase “I'm lovin' it” as a global brand platform and helped coordinate a more unified identity across national markets.
The campaign became notable for combining a short English phrase with music, celebrity appearances, and localized advertising. The associated song was recorded by Justin Timberlake, with production involving The Neptunes and vocals connected to the campaign's commercial release. The advertising rollout was global, but individual markets adapted executions and media.
The slogan is sometimes confused with the campaign's song or with the later “ba da ba ba ba” vocal tag. They are related parts of the same branding effort, but the answer to this question is the agency credited with creating the campaign concept. McDonald's continues to use the phrase as one of its most recognizable brand lines.