Aimed at millennials, the campaign positions what it calls Reese’s "slightly wrong but oh-so right" peanut butter and chocolate flavour combination as the ultimate indulgence.
The campaign, which is now live, will run across Facebook, Instagram, Snapchat and YouTube, throughout 2016.
The campaign features videos and images of millennials enjoying Reese’s treats in a series of unusual ways, carrying the strapline #Sorrynotsorry.
UM London developed the media strategy for the campaign and will handle all digital buying and social media. Arnold KLP was responsible for creative strategy, idea and execution.
Houssam Chehabeddine, EMEA general manager, The Hershey Company, said: "Our partnership with UM is based on the common vision we have for Reese’s potential in the UK. We’re confident that this campaign sharply reflects this vision and allows Reese’s to reach new heights in a very mature and competitive market."
Ben Reilly, group business director, UM London, added: "We’re proud to be working with Hershey’s on this digital launch for Reese’s in the UK. The brand is a sleeping giant, and with our commitment to blurring the lines between media and creativity, data and content, and science and art, we can help propel Reese’s forward in the coming years."