Low-dimensional magnetic materials with spin-$12$ moments can host a range of exotic magnetic phenomena due to the intrinsic importance of quantum fluctuations to their behavior. Here, we report the structure, magnetic structure and magnetic properties of copper(II) thiocyanate, Cu(NCS)$2$, a one-dimensional coordination polymer which displays low-dimensional quantum magnetism. Magnetic susceptibility, electron paramagnetic resonance (EPR) spectroscopy, $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}$C magic-angle spinning nuclear magnetic resonance (MASNMR) spectroscopy, and density functional theory (DFT) investigations indicate that Cu(NCS)$2$ behaves as a two-dimensional array of weakly coupled antiferromagnetic spin chains ($J2=133(1)$ K, $\alpha =J1/J2=0.08$). Powder neutron-diffraction measurements confirm that Cu(NCS)$2$ orders as a commensurate antiferromagnet below $TN=12$ K, with a strongly reduced ordered moment (0.3 $\mu B$) due to quantum fluctuations.