In this chapter we introduce and describe the notion of resilience for networked computer systems. Central to our viewpoint is that such systems need to be designed and engineered to have resilience as a major property. This is in contrast to systems found in nature that may already have resilience, in some cases through a process of evolution. The networked systems that we focus on here will generally be built using Internet technologies, which we briefly introduce. Engineered systems also require attention to their people and organizational aspects in order to produce a resilient outcome. Therefore, the material we present here is intended to combine the technological, organizational, and people aspects of resilient systems design and operation, with reference to utility networks – specifically to an electricity distribution case study. While the field of engineered resilience is advancing quickly, and involves multiple systems, much of what we say in this chapter still remains in the research phase, and has yet to be widely adopted in practice.