She will be replaced in the role by Bouygues veteran Philippe Bernard who has 30 years experience at the company.
He joins after a difficult few years at the company, which reported accumulated losses in 2023 and 2022 totalling just over £100m.
Viala was appointed Chair in 2016 and took on the additional CEO role last year when Rob Bradley retired from the business as part of a restructure.
Pierre-Eric Saint-André, Bouygues Construction’s Deputy Chief Executive Officer, said: “Over the last eight years, Fabienne has led Bouygues UK with resilience, passion, and tenacity.
“Championing sustainable construction and fostering diversity and inclusion, Fabienne has transformed Bouygues UK and positioned it as a leading construction and property development company in the United Kingdom, leaving a lasting impact.”
Viala added: “Leading Bouygues UK has been an immense honour. I thank my talented and dedicated colleagues for their invaluable support and wish the company every success.”