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This category (and within its own specific purpose, the analogous Category:Year of death unknown) is intended for placement in biographical entries about deceased individuals, primarily from antiquity (although, in some cases, reaching into the 19th century) whose year of birth is lost to history and never likely to be known. "Year of birth unknown" will also be applicable to many individuals from the less-remote past who gained varying degrees of notability at some points in their lives, but were born in times and under circumstances which precluded the recording and/or preservation of historical data.
Except for specific rare circumstances (such as birth in a remote region where no records were/are kept) which should be elucidated within the pertinent biographical entry, this category is not meant to include individuals who are currently in Category:Living people or Category:Possibly living people, as well as historically recent individuals who are no longer alive, but whose year of birth is presumed to have been recorded and could be researched. All individuals who are in those categories should be included in Category:Year of birth missing.
In the case of living subjects of biographical articles, please use Category:Year of birth missing (living people).
This category and categories Date of birth missing and Date of birth unknown (each of the "Date" categories indicates the presence of the year of birth, but the absence of the month and day) are intended to be mutually exclusive.
NOTE: Article-page categories which delineate the precise decade or century of the pertinent individual's birth, such as Category:1070s births or Category:11th-century births, specify additional data and are not intended as substitutes for "Year of birth unknown", which is an all-encompassing category.
Related categories 
- Category:Year of birth uncertain
- Category:Year of birth missing
- Category:Year of birth missing (living people)
- Category:Date of birth missing
- Category:Date of birth missing (living people)
- Category:Date of birth unknown
- Category:Place of birth missing
- Category:Place of birth missing (living people)
- Category:Place of birth unknown
- Category:Year of death missing
- Category:Year of death unknown
- Category:Date of death missing
- Category:Date of death unknown
- Category:Place of death missing
- Category:Place of death unknown
See also 
- Category:Living people
- Category:Possibly living people
- Category:Missing people
- Category:Dead people
- Category:Missing middle or first names
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