Alexandru (died on 26 July 1496) was the first-born son of Stephen III of Moldavia and his heir apparent. He participated in his father's fights against the Ottoman Empire and Wallachia from the late 1470s. He had his own court in Bacău from the early 1480s. He was made Stephen III's co-ruler in or before 1490. He predeceased his father.
Alexandru was the first-born son of Stephen III of Moldavia. His mother's identification is uncertain, because she may have been either one Mărușca (or Mărica), or Evdochia of Kiev, according to historian Jonathan Eagles. Assuming that Mărușca was Stephen's concubine, Eagles proposes that Alexandru could have been an illegitimate son. On the other hand, Stephen's charter of grant to the Hilandar Monastery on Mount Athos names Alexandru as one of the children of Stephen and Evdochia of Kiev. Consequently, according to Eagles, it is also possible, that Stephen fathered two sons named Alexandru, and his co-ruler was Evdochia's son. If Alexandru was Mărușca's son, he must have been born between 1457 and 1463; if Evdochia was his mother, he must have been born between 1463 and 1467.
Alexandru participated in the Battle of Valea Albă in 1476, according to an inscription at the Church of Saint Michael in Războieni. An inscription at the Church of Saint Procopius in Milișăuți recorded that Alexandru also fought alongside his father against Basarab the Younger at Râmnicu Vâlcea in 1481. Around that time, Alexandru, established his own court at Bacău. He allegedly administered the Lower Country (the southern region of Moldavia), according to Eagles. In the 1480s, he only referred to himself as his father's son, showing that he was still not regarded his father's co-ruler.