He replaces Eileen Naughton who moved to California to become vice-president of people operations in July.
Harris has been based in Dublin, in charge of the sales teams for large customers across EMEA. He will relocate to London for the new role.
He has been at Google for more than 11 years, joining as senior director for large customer sales for EMEA.
Fionnuala Meehan, vice-president of EMEA for Google marketing solutions, has been appointed Google site lead in Ireland alongside her existing role. The additional responsibility means she will look after Google’s operations and relationships in Ireland.
Matt Brittin, president of the EMEA business and operations at Google, said: "Over the last few years, I’ve had the privilege of seeing Ronan and Fionnuala build tremendous teams and operations that help businesses and publishers grow across EMEA. With that experience, we have a great leader in Ronan for the UK and Ireland business at a pivotal time and an inspirational leader in Ireland in Fionnuala."