Chiral magnets with Dzyaloshinskii–Moriya interaction host topological spin textures that generate emergent transport. We report a comprehensive study of ${\mathrm{Mn}}_{1/3}\mathrm{Nb}{\mathrm{S}}_2$, a less-understood member of the ${\mathrm{T}}_{1/3}\mathrm{M}{\mathrm{S}}_2$ chiral helimagnet family. Small-angle neutron scattering confirms a chiral helimagnetic ground state with a long helical period of 300 nm, indicating weak DMI. Under a $c$-axis field, the system evolves through a chiral conical phase (CCP) before reaching the forced ferromagnetic state; a pronounced topological Hall effect (${\rho }_{xy}^T\sim 70$ nΩ cm) emerges in the CCP. Detailed analysis shows that THE in CCP phases is dominated by a fluctuation-driven mechanism: thermal magnon excitations generate net scalar spin chirality even when static $〈\chi 〉$ vanishes. The intrinsic lattice chirality ($\mathrm{P}{6}_{3}22$) and DMI break left/right magnon degeneracy, allowing a longitudinal field alone to produce an imbalance. This accounts for the strong temperature dependence, boundary enhancement, and comparable topological Hall conductivity ${\sigma }_{xy}^T$ ($\sim 30{\left(\mathrm{\Omega }\mathrm{cm}\right)}^{-1}$) of ${\mathrm{Mn}}_{1/3}\mathrm{Nb}{\mathrm{S}}_2$ versus well-known CSL ${\mathrm{Cr}}_{1/3}\mathrm{Nb}{\mathrm{S}}_2$ ($\sim 6.5{\left(\mathrm{\Omega }\mathrm{cm}\right)}^{-1}$) despite much weaker DMI in the former. Our results establish ${\mathrm{Mn}}_{1/3}\mathrm{Nb}{\mathrm{S}}_2$ as a distinct platform for fluctuation-driven topological transport in weakly DMI, strongly anisotropic chiral magnets.

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• Angular-dependent magnetoresistance
• Helicoidal magnetic texture
• Magnetic phase transitions
• Topological Hall effect
• Chiral magnets
• Noncollinear magnets
• Crystal growth
• Magnetization measurements
• Resistivity measurements
• Small angle neutron scattering