The Kavli Institute for Cosmological Physics (KICP) at the University of Chicago is hosting a workshop this summer on the origin of the non-thermal extragalactic backgrounds. The goal is to bring together observers and theorists representing all the high-energy wavebands and particles: radio, GeV and TeV gamma rays, and extragalactic cosmic rays and neutrinos. Topics will include isotropic diffuse intensity measurements, resolved extragalactic source populations and their collective contributions below the individual source detection threshold, anisotropies, and propagation effects and secondary cascades.

Example focus questions:
* Is there a coherent scenario which explains all the current observations in terms of established extragalactic source populations?
* What are the next steps (experimental + theoretical) to move past current uncertainties/degeneracies?

We are planning a three-day workshop for about fifty participants convening on the campus of the University of Chicago. Each day will consist of plenary presentations with plenty of time for discussion in large and/or small groups.