Abia is a state in the Southeastern region of Nigeria. The state's capital is Umuahia and its most populous city is Aba. The legislature is the Abia State House of Assembly.

Abia is bordered the west by Imo, east by Cross River, south by Rivers, northwest by Anambra and northeast by Enugu and Ebonyi. The state is divided between the Niger Delta swamp forests in the south and the Cross–Niger transition forests. The Imo and Aba Rivers flows along the state's western and southern borders respectively. Known for producing crude oil and natural gas, Abia ranks the eighth by Human Development Index since 2019.

The name "Abia" is an abbreviation of Abia state's four densely populated regions Aba, Bende, Isuikwuato, and Afikpo. Abia's slogan is "God's own state". Abia is one of the 36 states in Nigeria, and has seventeen Local government areas. It was created on 27 August 1991 out of Imo State by General Ibrahim Babangida, and it is located in the south-eastern part of Nigeria with Umuahia as the capital, and Aba as the commercial city.

Abia State's history begins as part of the Aro Confederacy until its defeat in the early 1900s by the British troops during the Anglo-Aro War. After the war, the area was incorporated into the Southern Nigeria Protectorate of British Nigeria. After Nigeria's independence in 1960, Abia became part of the Eastern Region until 1967 before the region was split, and it became part of the East Central State. The Eastern Region attempted to secede in Nigerian Civil War with Abia as part of the secessionist state of Biafra. After the war and the then reunification of Nigeria, the East Central State was merged until 1976 when Imo including Abia, was formed by Murtala Muhammed. Eastern Imo would later become the old Abia State after a split. In 1996, part of Abia's northeast was removed to form a part of the new Ebonyi.

The Igbo people make up 95% of the state's population and the official language is Igbo. Ibibio is also spoken in some parts of the state especially in Arochukwu. There are over 3 million Christians. Catholic Hierarchy analyses that there are 689,668 Catholics (2020) in Diocese of Umuahia with over 70 parishes, and Aba Diocese with over 90 parishes, both suffragans of the Archdiocese of Owerri.

Abia State was created from Imo State by Ibrahim Babangida on 27 August 1991.

Abia State occupies about 4902 square kilometres. It is bounded on the north and northeast by the states of Enugu for about 25 km, and Ebonyi for 70 km (43 miles), Cross River State for about 52 km (partly across Cross River) and Akwa Ibom State for 151 km (94 miles) to the east and southeast respectively, Rivers State to the south and west for 87 km (54 miles), Imo State and Anambra to the west for to the west in the vicinity of the Imo River) for about 18 km and about 104 km respectively. The southernmost part of the State lies within the Niger Delta Swamp Forests, while the rest of the state, lies within the Cross–Niger transition forests. The southern portion gets heavy rainfall of about 2,400 millimetres (94 in) per year and it is intense between the months of April through October. The most important rivers in Abia State are the Imo and Aba Rivers which flow into the Atlantic Ocean through Akwa Ibom State.

Municipal solid waste management (MSWM) deals with the collection, storing, treatment and disposal of solid waste, to ensure that it does not affect humans, living things and the environment at large. There are factors that influence Municipal solid waste generation such as income level, local climatic condition, urbanization and economic development. MSW in Aba, Abia State is classified into;