Which performer was featured in McDonald’s original 2003 “I’m Lovin’ It” campaign song?

Justin Timberlake was featured in McDonald’s original 2003 “I’m Lovin’ It” campaign song.

The campaign was built around a pop-oriented musical identity rather than a conventional spoken commercial line. Timberlake appeared in the associated song and music video, helping connect the fast-food brand with contemporary popular culture. The phrase and melody were then adapted for McDonald’s advertising around the world.

The campaign had several creative contributors. The slogan’s musical development is often discussed alongside producer Pharrell Williams and rapper Pusha T, whose involvement has led to different simplified versions of the story. Timberlake’s role, however, was as the featured performer associated with the released campaign song.

This question concerns the campaign song, not the person credited with writing every part of the jingle or the agency that developed the international advertising strategy. Those are separate production roles.