Alexander Joseph, known as Alexander of Battenberg, was the first prince (knyaz) of the autonomous Principality of Bulgaria from 1878 until his abdication in 1886.

Knyaz or knez, also knjaz, kniaz is a historical Slavic title, used both as a royal and noble title in different times of history and different ancient Slavic lands. It is usually translated into English as prince, depending on specific historical context and the potentially known Latin equivalents of the title for each bearer of the name. These translations probably derive from the fact that the title tsar was often treated as equivalent to "king" by European monarchs. In Latin sources the title is usually translated as princeps, but the word was originally derived from the common Germanic *kuningaz (king).