Lythgoe has been the global head of business development since January 2016 and the UK and EMEA head of marketing for the past four years. Her new role adds global marketing responsibilities.
"Sam has been an integral part of the company for 20 years now," said H+K global president Lars Erik Grønntun. "Throughout our time working together, she has taken the business development and marketing teams from strength to strength, working tirelessly to cement H+K’s position as a trusted client partner and a strategic, creative and innovative leader in the industry."
"I have no doubt that she will continue to go above and beyond to make the company excel in this area as One H+K."
Prior to taking on a business development role, Lythgoe started the consumer tech practice in H+K’s London office and led a number of clients, including TomTom and BT.
Over the past decade, H+K said Lythgoe has increased the agency’s business conversion by embedding the agency’s ‘purpose-driven approach’.
She has also led internal programs such as H+K HER, developed to provide support and inspiration to female employees throughout their careers.
Commenting on her appointment, Lythgoe said: "I am thrilled about the future of H+K as we continue working towards a stronger, unified global agency. Our One H+K approach, underpinned by the Fifth Seat proposition, enables us to deliver services in a clear and compelling way. We have the tools and expertise to support our clients, whenever and wherever is needed."