  Nearby galaxies provide populations of stellar and non-stellar sources at a
common distance and in quantifiable environments. All are observed through the
Milky Way foreground, with varying degrees of contamination that depend on
observed Galactic latitude and the distance and size of the target galaxy. This
work uses Gaia Data Release 3 (DR3) to identify foreground sources via
astrometric measurements and thus quantify foreground contamination for a large
sample of nearby galaxies. There are approximately half a million Gaia sources
in the directions of 1401 galaxies listed in the Local Volume Galaxy catalogue
(D<11 Mpc), excluding the largest Local Group galaxies. About two thirds of the
Gaia sources have astrometric properties consistent with foreground sources;
these sources are brighter, redder, and less centrally-concentrated than
non-foreground sources. Averaged over galaxies, foreground sources make up 50
per cent of Gaia sources at projected radius r50=1.06*a26, where a26 is the
angular diameter at the B=26.5 isophote. Foreground sources make up 50 per cent
of Gaia sources at apparent magnitude m(G,50)=20.50. This limit corresponds to
the tip of the red giant branch absolute magnitude at D = 450 kpc, and to the
globular cluster luminosity function peak absolute magnitude at 5 Mpc. Gaia
data provide a powerful tool for removing foreground contamination in stellar
population studies of nearby galaxies, although Gaia foreground removal will be
incomplete beyond distances of 5 Mpc.
