Increasingly key elements of society – defense, energy, transportation, water resources, telecommunications, finance, others – critically depend on the coordinated functioning of multiple independent systems which are designed, operated, and maintained by separate organizations with their own objectives, stakeholders, operating models, and constraints. These ‘systems of systems’ (SoS) by their very nature are complex, dynamic, and not only depend on multiple autonomous engineered systems which may be complex systems themselves, but also on the complex human and organizational environments in which they are developed and operated. Over the past decade there has been steadily growing international interest in application of systems engineering to SoS. Beginning with attention by the U.S. defense community, interest in systems engineering for SoS has expanded with research and applications in a wide array of domains both in the U.S. and internationally. This presentation looks at the growing attention to systems of systems across the systems engineering community, characterizes the persistent challenges that SoS pose for systems engineering and the opportunities for SoS engineering given the increasing interdependencies of today’s socio-technical systems.