BAC or Bac may refer to:
Bač (Serbian Cyrillic: Бач, [bâːtʃ]) is a town and municipality in South Bačka District of Vojvodina, Serbia. The town has a population of 5,399, while Bač municipality has 14,405 inhabitants. The Bačka region was named after the town of Bač.
In Serbian, the town is known as Bač (Бач); in Slovak as Báč; in Croatian (Šokac) as Bač; in Hungarian as Bács; in German as Batsch; in Latin as Bach or Bacs; and in Turkish as Baç. Along with Serbian, Slovak and Hungarian languages are also in official use in the municipality administration.
In the 9th-10th century, name of the town was Bagasin. In 1154, the Arab geographer Idrisi mention it under name Bakasin and claim that "it is a famous city that was mentioned among old big cities".
The current name of the town was first recorded in 1094. In 1111 the parish was mentioned as Bache. This name probably derived from the same personal name. In Serbian this name is written as Bač (Бач), in Hungarian as Bács, and in Romanian as Baci, although the Romanian population used this word as a title rather than as a name. The name is of uncertain origin and its existence was recorded among Vlachs, Slavs and Hungarians in the Middle Ages. The origin of the name could be Paleo-Balkanic,Romanian, Slavic, or Old Turkic.