By

By or BY means the following:

* by or bye, a free pass through a round of competition in a tournament
* Bavaria (BY), official abbreviation of the German federal state Bavaria
* By, Doubs, a commune in the Doubs "département" of France
* Belarus (BY), WMO and 2-letter ISO country code
** .by, the ccTLD for Belarus
* Britannia Airways IATA airline code
* Budget Year (BY), a synonym for Fiscal Year
* Burundi (BY), FIPS Pub 10-4 and obsolete NATO digram country code
* By, John Lieutenant-Colonel, 19th century British military engineer famous for his work in Canada
* Byelorussian Soviet Socialist Republic, obsolete (1992) 2-letter ISO country code
* Thomsonfly IATA airline code