The Pirai River may refer to:

• the Piray River in Bolivia
• the Piraí River (Paraná), a river of Paraná state in southern Brazil
• the Piraí River (Rio de Janeiro), a river of Rio de Janeiro state in southeastern Brazil
• the Piraí River (Santa Catarina), a river of Santa Catarina state in southeastern Brazil
• the Pirai River (India), a river of India

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