Harris will oversee Stripe’s strategic planning process across existing and new clients, and joins the agency's London management board.
Harris worked at Luchford for more than six years and has served in senior roles including chief strategy officer and managing partner.
She previously worked at Golley Slater, Hill+Knowlton and Brave PR, among other agencies.
Harris joins following a record year at Stripe, during which the firm picked up new clients TGI Fridays, Grosvenor Casinos, Legoland Windsor Resorts, Mecca Bingo, Hollywood Bowl and Battersea Power Station.
"With over 20 years of experience working with some of the world’s leading consumer brands, both in the UK and internationally, Lou is a brilliant addition to the team," Stripe Communications London managing director Chris Stevenson said.
"In particular, the experience she has built up in recent years in travel, leisure, hospitality and luxury, opens up a wealth of opportunities for us to explore."
Harris said: “I’m hugely excited and honoured to join such a fast-growing, highly skilled and dynamic agency. I was attracted to Stripe for its impressive client portfolio and because of the team’s ambition and passion to be the best. I look forward to adding a new dimension to this already incredible agency.”