The launch of the London-based office will complete the global presence of PPR, which is already established in the Asia Pacific and US regions.
Fieldhouse will take the position of chief executive of the fledgling office, moving from FTI where she headed international corporate communications.
Before that she spent five years at Edelman and held posts at Kinross & Render and BSMG Worldwide.
On of the first products launched by the agency will be PSS Media – a video distribution platform for brands to communicate with clients, staff and investors.
Fieldhouse said: ""These are both exciting and challenging times for our industry, and as someone who has always believed in the power of integrated communications I am excited to be building a business that can harness the right people, skills, expertise, services and tools to really deliver on this promise."
Following the launch of the UK office this month the agency will open offices in France, Germany and the Middle East early next year, with plans to roll out across other markets during the next 18 months.
Peter Stringham, Y&R Group chairman and chief executive officer, said: "PPR is the perfect agency partner for clients seeking the energy and entrepreneurial spirit of a new, fresh brand that has a reputation for innovation and leadership."
PPR has most recently been awarded a three-country brief across the UK, France and Germany for Microstrategy, with other clients expected to be announced in the New Year.