By or BY may refer to:
The Byzantine Empire, also referred to as the Eastern Roman Empire, was the continuation of the Roman Empire in the East during Late Antiquity and the Middle Ages, when its capital city was Constantinople (modern-day Istanbul, which had been founded as Byzantium).
The bystander effect, or bystander apathy, is a social psychological phenomenon in which individuals are less likely to offer help to a victim when other people are present.
Bye Bye Birdie is a stage musical with a book by Michael Stewart, lyrics by Lee Adams and music by Charles Strouse.
The Byzantine Rite, also known as the Greek Rite, Rite of Constantinople or Constantinopolitan Rite, is the liturgical rite currently used by the Eastern Orthodox Church and certain Eastern Catholic Churches.
Byun Baek-hyun (born May 6, 1992), better known mononym as Baekhyun, is a South Korean singer and actor.
The Byzantine–Sasanian War of 602–628 was the final and most devastating of the series of wars fought between the Byzantine (Eastern Roman) Empire and the Sasanian Empire of Persia.
Bydgoszcz /ˈbɪdɡɒʃtʃ/ (Polish pronunciation: [ˈbɨdɡɔʂt͡ʂ], German: Bromberg [ˈbʁɔmbɛɐ̯k], Latin: Bydgostia) is a city in northern Poland, on the Brda and Vistula rivers.