Hebrides
May 14 Felix Mendelssohn's concert overture "Hebrides" premieres in London, England
- May 21 First US Democratic National Convention, is held in Baltimore
- May 24 The First Kingdom of Greece is declared in the London Conference
- May 30 Evariste Galois give his theory on free assembly (dies in duel May 31)
- May 30 The Rideau Canal in eastern Ontario is opened. Oldest continuously operated canal system in North America.