- Oct 3 The Treaty of Nissa is signed by the Ottoman Empire and Russia at the end of the Russian-Turkish War, 1736-1739.
- Oct 19 England declares war on Spain [OS=Oct 30]
Declaration of War
Oct 23 War of Jenkins' Ear starts: British Prime Minister, Robert Walpole, reluctantly declares war on Spain
- Oct 30 Great Britain declares war on Spain: War of Jenkins' Ear [NS=Oct 19]