  The preponderance of matter over antimatter in the early universe, the
dynamics of the supernovae that produced the heavy elements necessary for life,
and whether protons eventually decay -- these mysteries at the forefront of
particle physics and astrophysics are key to understanding the early evolution
of our universe, its current state, and its eventual fate. The Deep Underground
Neutrino Experiment (DUNE) is an international world-class experiment dedicated
to addressing these questions as it searches for leptonic charge-parity
symmetry violation, stands ready to capture supernova neutrino bursts, and
seeks to observe nucleon decay as a signature of a grand unified theory
underlying the standard model.
  The DUNE far detector technical design report (TDR) describes the DUNE
physics program and the technical designs of the single- and dual-phase DUNE
liquid argon TPC far detector modules. This TDR is intended to justify the
technical choices for the far detector that flow down from the high-level
physics goals through requirements at all levels of the Project. Volume I
contains an executive summary that introduces the DUNE science program, the far
detector and the strategy for its modular designs, and the organization and
management of the Project. The remainder of Volume I provides more detail on
the science program that drives the choice of detector technologies and on the
technologies themselves. It also introduces the designs for the DUNE near
detector and the DUNE computing model, for which DUNE is planning design
reports.
  Volume II of this TDR describes DUNE's physics program in detail. Volume III
describes the technical coordination required for the far detector design,
construction, installation, and integration, and its organizational structure.
Volume IV describes the single-phase far detector technology. A planned Volume
V will describe the dual-phase technology.
