  We report the low temperature magnetic properties of the DyScO$_3$
perovskite, which were characterized by means of single crystal and powder
neutron scattering, and by magnetization measurements. Below
$T_{\mathrm{N}}=3.15$ K, Dy$^{3+}$ moments form an antiferromagnetic structure
with an easy axis of magnetization lying in the $ab$-plane. The magnetic
moments are inclined at an angle of $\sim\pm{28}^{\circ}$ to the $b$-axis. We
show that the ground state Kramers doublet of Dy$^{3+}$ is made up of primarily
$|\pm 15/2\rangle$ eigenvectors and well separated by crystal field from the
first excited state at $E_1=24.9$ meV. This leads to an extreme Ising
single-ion anisotropy, $M_{\perp}/M_{\|}\sim{0.05}$. The transverse magnetic
fluctuations, which are proportional to $M^{2}_{\perp}/M^{2}_{\|}$, are
suppressed and only moment fluctuations along the local Ising direction are
allowed. We also found that the Dy-Dy dipolar interactions along the
crystallographic $c$-axis are 2-4 times larger than in-plane interactions.
