Abo may refer to:

• Åbo, the Swedish name for Turku in Finland.
• In Australia, an abbreviation of Aborigine (ethnic slur).
• Abo (historic place), a registered historic place in New Mexico.
• ABO blood group system
• American Board of Opticianry
• Accumulated Benefit Obligation
• Abo of Tiflis, a Christian saint

The ABO blood group system is the most important blood type system (or blood group system) in human blood transfusion. The associated anti-A antibodies and anti-B antibodies are usually IgM antibodies, which are usually produced in the first years of life by sensitization to environmental substances such as food, bacteria and viruses. ABO blood types are also present in some animals, for example cows and sheep, apes such as chimpanzees, bonobos and gorillas.

Turku (IPA: , Swedish: ), founded in the 13th century, is the oldest and fifth largest city in Finland, with a population of 175,354 (as of 2006). Located [1] at the mouth of the Aura river in the southwest of the country, it is the capital city of both the region of Finland Proper and the province of Western Finland, as well as being the centre of the country's third largest urban area, with around 300,000 inhabitants. Turku has one of the largest Finland-Swedish populations in the country. Due to its location, the Port of Turku is one of the busiest seaports in Finland with around 3.7 million passengers per year[2].