Buyin may refer to:

• Buyin, an alternate name of Buin Zahra, a city in Iran
• Buyin, Zanjan, a village in Zanjan Province, Iran
• BUYIN, a procurement joint-venture by Deutsche Telekom and Orange
• "Buy-in", a poker term, see: Glossary of poker terms#buy-in
• The purchase of a company by a new manager or management team, see Management buy-in

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• Prasco Laboratories
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