  The earliest galaxies are expected to emerge in the first billion years of
the Universe during the Epoch of Reionization. However, both the spectroscopic
confirmation of photometrically-selected galaxies at this epoch and the
characterization of their early dynamical state has been hindered by the lack
of bright, accessible lines to probe the velocity structure of their
interstellar medium. We present the first ALMA spectroscopic confirmation of
such sources at z > 6 using the far-infrared [C II]{\lambda}157.74{\mu}m
emission line, and, for the first time, measurement of the velocity structure,
for two galaxies at z = 6.8540+/-0.0003 and z = 6.8076+/-0.0002. Remarkably,
the [C II] line luminosity from these galaxies is higher than previously found
in `normal' star-forming galaxies at z > 6.5. This suggests that we are
sampling a part of the galaxy population different from the galaxies found
through detection of the Ly{\alpha} line. The luminous and extended [C II]
detections reveal clear velocity gradients that, if interpreted as rotation,
would suggest these galaxies have turbulent, yet rotation-dominated disks, with
similar stellar-to-dynamical mass fractions as observed for H{\alpha} emitting
galaxies 2 Gyr later at cosmic noon. Our novel approach for confirming galaxies
during Reionization paves the way for larger studies of distant galaxies with
spectroscopic redshifts from ALMA. Particularly important, this opens up
opportunities for high angular-resolution [C II] dynamics in galaxies less than
one billion years after the Big Bang.
