The campaign will be initially launched in the US market, before continuing in 17 other markets including Brazil, Tunisia and the UK.
The activity is based on the theme "life can't wait" and challenges female consumers to describe personal stories, involving a life-changing moment, on camera.
The stories will be shortlisted and shown online where consumers can vote for their favourite video.
The stories with the most votes will be re-made into a short docu-drama starring the real girl in addition to a 30-second TV ad.
The stories will be sourced from a series of regional workshops in each market called 'Girl Camp'.
The wider Sunsilk campaign also includes contributions from Brand Think Tank in Paris, London-based Salt, digital agency AKQA and media agency MindShare.
Jamie Anley, chief executive of Jam, said: "It's awesome that this brand has the courage and vision to embark on such a creative and ambitious project as part of the global brand re-launch.
"It is the future beyond advertising and this is the most significant uptake of this approach to have ever happened -- a sign of great things to come in the near future."
Andrei Gemenanu, the global brand director of Unilever, added: "We are delighted to be working with JAM who come with a unique perspective, skill set and approach to building future facing brands and this fits well with our culture and where we want to go."