The key problems in the development of fusion technology as a possible energy source are linked to the understanding of the behavior of materials, components and systems under working conditions of the fusion environment. As a consequence, it has been recognized that a neutron source able to produce neutrons with a fusion-like energy spectrum associated with a gamma radiation field is necessary. In addition, this source must have an irradiation volume large enough to allow the statistically relevant characterization of the macroscopic properties of materials and components, a cumulated damage level above that expected in the reactor operational lifetime, and an intensity strong enough to allow slightly accelerated testing. In this publication we review the main possible ideas for a fusion-like neutron source, present the concept of the neutron source based on the d-Li reaction, and discuss the stepped approach which led to the design of the DEMO-oriented neutron source (DONES). The mission and top-level specifications of DONES are presented and related to the different DEMO requirements. In a dedicated section, the availability of DONES and the compatibility of its parameters for the experiments in which the main tritium breeding concepts—solid and liquid metal based—can be validated are described. Apart from the development of fusion technology, DONES has the potential to become a multidisciplinary neutron science facility. We discuss the concept of a DONES neutron time-of-flight (TOF-DONES) experiment for nuclear physics experiments such as cross section measurements and nuclear technologies studies (fusion and fission), astrophysics and particle physics. Last but not least, some considerations for a preliminary irradiation programme at DONES are presented to demonstrate a possible timeline for the exploitation of the facility to tackle the foremost problems of DEMO and fusion reactor technology.