• O
• Oats
• Obelisk
• Obelus
• Obrenovac ⚐
• Occitan
• Occult
• Octopus heart
• Odal
• Odin
• Offaly ⚐
• Ojo de Dios
• Old Catholic Church +
• Old Glory
• Old Rugged
• Old Testament Cross
• Olga
• Olive Branch
• Omaha ⚐
• Omaha Orange
• Oman ⚐
• Omega
• Onch
• Ondée
• Onk
• Ontario ⚐
• Oorlogskruis
• Ora et Labora
• Orange
• Orb
• Order of Christ
• Order of Preachers +
• Order of Saint Camillus +
• Order of St. Luke
• Ordinaria
• Oreo (seriously?)
• Original Church of God
• Orion
• Orkney ⚐
• Ormso
• Ornate
• Orthodox
• Orthodox Church in America +
• Orthodox Church in Italy +
• Orthodox Church of Greece (Holy Synod in Resistance) +
• Orthodox Ohrid Archbishopric +
• Other
• Ouder-Amstel ⚐
• Oundy (Oundé)
• Our Father
• Outline
• Own
• Oxford Martyrs
• Oyster

⚐ denotes cross on the flag of a nation or region
+ denotes cross on the emblem of a church or denomination

There are countless more. We are continually updating information on all these crosses and adding more as they become known to us.