51st meridian may refer to:

• 51st meridian east, a line of longitude east of the Greenwich Meridian
• 51st meridian west, a line of longitude west of the Greenwich Meridian

• Benevolent Dictator For Life
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• Benewah County Courthouse
• BeNEX
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• Beneš-Mráz Be-150
• Beneš-Mráz Be-150 Beta-Junior
• Beneš-Mráz Be-501