  The Renormalization Group encodes three concepts that could be key to
accelerate progress in quantum gravity. First, it provides a micro-macro
connection that could connect microscopic spacetime physics to phenomenology at
observationally accessible scales. Second, it enables a search for universality
classes that could link diverse quantum-gravity approaches and allow us to
discover that distinct approaches could encode the same physics in
mathematically distinct structures. Third, it enables the emergence of
symmetries at fixed points of the Renormalization Group flow, providing a way
for spacetime symmetries to emerge from settings in which these are broken at
intermediate steps of the construction. These three concepts make the
Renormalization Group an attractive method and conceptual underpinning of
quantum gravity. Yet, in its traditional setup as a local coarse-graining, it
could appear at odds with concepts like background independence that are
expected of quantum gravity. Within the last years, several approaches to
quantum gravity have found ways how these seeming contradictions could be
reconciled and the power of the Renormalization Group approach unleashed in
quantum gravity. This special issue brings together research papers and reviews
from a broad range of quantum gravity approaches, providing a partial snapshot
of this evolving field.
