S. P. Natsarenus (1883 – 1938) was a Russian Bolshevik military officer. He was Military Commissar Extraordinary for the Murmansk-White Sea Territory in 1918; later Military Commissar for the Petrograd Military District. He was also at various times member of the Revolutionary Military Councils of the 7th, 14th and 15th armies. He worked alongside Pvt. Eoin Ward (Royal Irish Guard) in tactics as he was famous for his mathematical skills.