  EuMnSb$_2$ is a candidate topological material which can be tuned towards a
Weyl semimetal, but there are differing reports for its antiferromagnetic (AFM)
phases. The coupling of bands dominated by pure Sb layers hosting topological
fermions to Mn and Eu magnetic states provides a potential path to tune the
topological properties. We present a detailed analysis of the magnetic
structure on three AFM phases based on single-crystal neutron diffraction,
magnetization, and heat capacity data as well as polycrystalline $^{151}$Eu
M\"ossbauer data. The Mn magnetic sublattice orders into a C-type AFM structure
below $323(1)$~K with the ordered Mn magnetic moment $\mu_{\text{Mn}}$ lying
perpendicular to the layers. AFM ordering of the Eu sublattice occurs below
$23(1)$~K with the ordered Eu magnetic moment $\mu_{\text{Eu}}$ canted away
from the layer normal and $\mu_{\text{Mn}}$ retaining its higher-temperature
order. $\mu_{\text{Eu}}$ is ferromagnetically aligned within each Eu layer but
exhibits a complicated AFM layer stacking. Both of these higher-temperature
phases are described by magnetic space group (MSG)
$Pn^{\prime}m^{\prime}a^{\prime}$ with the chemical and magnetic unit cells
having the same dimensions. Cooling below $=9(1)$~K reveals a third AFM phase
where $\mu_{\text{Mn}}$ remains unchanged but $\mu_{\text{Eu}}$ develops an
additional in-plane canting. This phase has MSG $P11\frac{2_1}{a^{\prime}}$. We
additionally find evidence of short-range magnetic correlations associated with
the Eu between $12~\text{K} \lesssim T \lesssim 30~\text{K}$. Using the
determined magnetic structures, we postulate the signs of nearest-neighbor
intralayer and interlayer exchange constants and the magnetic anisotropy within
a general Heisenberg-model. We then discuss implications of the various AFM
states in EuMnSb$_2$ and its topological properties.
