  We describe the first public data release of the Dark Energy Survey, DES DR1,
consisting of reduced single epoch images, coadded images, coadded source
catalogs, and associated products and services assembled over the first three
years of DES science operations. DES DR1 is based on optical/near-infrared
imaging from 345 distinct nights (August 2013 to February 2016) by the Dark
Energy Camera mounted on the 4-m Blanco telescope at Cerro Tololo
Inter-American Observatory in Chile. We release data from the DES wide-area
survey covering ~5,000 sq. deg. of the southern Galactic cap in five broad
photometric bands, grizY. DES DR1 has a median delivered point-spread function
of g = 1.12, r = 0.96, i = 0.88, z = 0.84, and Y = 0.90 arcsec FWHM, a
photometric precision of < 1% in all bands, and an astrometric precision of 151
mas. The median coadded catalog depth for a 1.95" diameter aperture at S/N = 10
is g = 24.33, r = 24.08, i = 23.44, z = 22.69, and Y = 21.44 mag. DES DR1
includes nearly 400M distinct astronomical objects detected in ~10,000 coadd
tiles of size 0.534 sq. deg. produced from ~39,000 individual exposures.
Benchmark galaxy and stellar samples contain ~310M and ~ 80M objects,
respectively, following a basic object quality selection. These data are
accessible through a range of interfaces, including query web clients, image
cutout servers, jupyter notebooks, and an interactive coadd image visualization
tool. DES DR1 constitutes the largest photometric data set to date at the
achieved depth and photometric precision.
