Ferromagnetic single atom doped BP monolayers are proposed as electrocatalysts for lithium-sulfur batteries. Based on first-principles calculations, it is found that Fe-BP and Ni-BP monolayers exhibit higher electronic conductivity, and their adsorption ability for lithium polysulfides are significantly enhanced compared to the bare BP monolayer, which could effectively suppress the shuttling effect. Besides, the Fe-BP monolayer shows the lowest energy barrier for both sulfur reduction reaction and Li2S decomposition, with a low Li+ diffusion energy barrier of 0.25 eV. Based on these results, Fe-BP monolayer is suggested as a promising single-atom electrocatalyst for sulfur redox reactions which will show fast charge–discharge kinetics and long cycle life in lithium-sulfur batteries.