Post Proper Southside, also known as Post Proper South, Barangay 31, or simply Southside, is one of the 38 barangays of Taguig, Philippines. It is one of the ten Embo barangays, and one of the two Inner Fort Bonifacio barangays, the other one being the Post Proper Northside. It was established in 1972 as a settlement inside the Fort Bonifacio Military Reservation, and its territory is disputed with barangays Fort Bonifacio, Pinagsama, and Ususan. The barangay has multiple exclaves mostly within Palar Village and has settlements in the Consular Area in Lawton Avenue.