3rd meridian may refer to:

• 3rd meridian east, a line of longitude east of the Greenwich Meridian
• 3rd meridian west, a line of longitude west of the Greenwich Meridian
• The Third Principal Meridian in Illinois, United States, 89°10'15" west of Greenwich
• The Third Meridian of the Dominion Land Survey in Canada, 106° west of Greenwich

This disambiguation page lists articles associated with the title 3rd meridian.
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