Petar I may refer to:
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Petar I of Bulgaria (r. 927-969), Emperor (Tsar) of Bulgaria
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Petar I Petrović-Njegoš (1747–1830), Montenegrin ruler, metropolitan and saint
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Peter I of Serbia (1844–1921), Serbian king
See also
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Peter I (disambiguation) Peter I may refer to:
Religious hierarchs
* Saint Peter (c. 1 AD – c. 64–88 AD), a.k.a. Simon Peter, Simeon, or Simon, apostle of Jesus
* Pope Peter I of Alexandria (died 311), revered as a saint
* Peter I of Armenia (died 1058), Catholicos ...
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