  We measure the Sun's velocity with respect to the Galactic halo using Gaia
Early Data Release 3 (EDR3) observations of stellar streams. Our method relies
on the fact that, in low-mass streams, the proper motion of stars should be
directed along the stream structure in a non-rotating rest frame of the Galaxy,
but the observed deviation arises due to the Sun's own reflex motion. This
principle allows us to implement a simple geometrical procedure, which we use
to analyse 17 streams over a $\sim 3-30$ kpc range. Our constraint on the Sun's
motion is independent of any Galactic potential model, and it is also
uncorrelated with the Sun's galactocentric distance. We infer the Sun's
velocity as $V_{R,\odot}=8.88^{+1.20}_{-1.22}\,\rm{kms^{-1}}$ (radially towards
the Galactic centre), $V_{\phi,\odot}=241.91^{+1.61}_{-1.73}\,\rm{kms^{-1}}$
(in the direction of Galactic rotation) and
$V_{z,\odot}=3.08^{+1.06}_{-1.10}\,\rm{kms^{-1}}$ (vertically upwards), in
global agreement with past measurements through other techniques; although we
do note a small but significant difference in the $V_{z,\odot}$ component. Some
of these parameters show significant correlation and we provide our MCMC output
so it can be used by the reader as an input to future works. The comparison
between our Sun's velocity inference and previous results, using other
reference frames, indicates that the inner Galaxy is not moving with respect to
the inertial frame defined by the halo streams.
