Assystem S. A. provides engineering and infrastructure project management services worldwide. The company provides engineering services for the preparation, design, and construction of critical and complex infrastructure projects for public authorities and utility companies.

It also offers engineering, procurement, and construction management; project management consulting; industrial control system; siting and permit studies; research and analysis; systems engineering; project management; digital engineering; project control solutions; digital field services; and industrial data science, as well as compliance, safety and security services for nuclear, energy, transportation, defense, and buildings and infrastructure sectors. In addition, the company provides decommissioning and waste management services, and integration and maintenance services. Assystem S.

A. was formerly known as AssystemBrime S. A. and changed its name to Assystem S. A. in June 2005.

The company. was founded in 1966 and is headquartered in Courbevoie, France. Assystem S. A. is a subsidiary of HDL Development.