Agusan del Sur, officially the Province of Agusan del Sur, is a province in Caraga region, Mindanao, Philippines. Its capital is the municipality of Prosperidad. It is bordered on the northwest by Agusan del Norte and Misamis Oriental; east by Surigao del Sur; southeast by Davao Oriental; mid-south by Davao de Oro; southwest by Davao del Norte and, mid …Agusan del Sur, officially the Province of Agusan del Sur, is a province in Caraga region, Mindanao, Philippines. Its capital is the municipality of Prosperidad. It is bordered on the northwest by Agusan del Norte and Misamis Oriental; east by Surigao del Sur; southeast by Davao Oriental; mid-south by Davao de Oro; southwest by Davao del Norte and, mid-west by Bukidnon. It is the fourth largest province in the country in terms of area, with the size of 3,856 sq miles.