A fluid housing of a fluid treatment system of a fluid system has a housing part of plastic material that is provided with a receiving chamber for accommodating a fluid treatment component; an installation opening, closable by a closure housing part, for installing the fluid treatment component in the receiving chamber; and a housing connecting section to connect the housing part to the closure housing part. A housing fastening section is provided with which the fluid housing can be fastened to a holding component of the fluid system. An insert is at least partially introduced into the plastic material of the housing part. The insert is provided with a reinforcement region extending with sections thereof in the housing connecting section and is further provided with fastening region extending with sections thereof in the housing fastening section. A fluid treatment system with such a fluid housing is provided.