  The scientific potential of a wide field-of-view, and very-high duty cycle,
ground-based gamma-ray detector has been demonstrated by the current generation
of instruments, such as HAWC and ARGO, and will be further extended in the
Northern Hemisphere by LHAASO. Nevertheless, no such instrument exists in the
Southern Hemisphere yet, where a great potential lies uncovered for the mapping
of Galactic large scale emission as well as providing access to the full sky
for transient and variable multi-wavelength and multi-messenger phenomena.
Access to the Galactic Centre and complementarity with the CTA-South are other
key motivations for such a gamma-ray observatory in the South. There is also
significant potential for cosmic ray studies, including investigation of
cosmic-ray anisotropy. In this contribution I will present the motivations and
the concept of the future Southern Wide-Field Gamma-ray Observatory (SWGO), now
formally established as an international Collaboration and currently in R\&D
phase. I will also outline its scientific objectives.
