| 30121 | March 18 | Event | 1834 – Six farm labourers from Tolpuddle, Dorset, England are sentenced to be transported to Australia for forming a trade union. |
| 30122 | March 18 | Event | 1848 – March Revolution: In Berlin there is a struggle between citizens and military, costing about 300 lives. |
| 30123 | March 18 | Event | 1850 – American Express is founded by Henry Wells and William Fargo. |
| 30124 | March 18 | Event | 1865 – American Civil War: The Congress of the Confederate States adjourns for the last time. |
| 30125 | March 18 | Event | 1871 – Declaration of the Paris Commune President of the French Republic, Adolphe Thiers, orders the evacuation of Paris. |
| 30126 | March 18 | Event | 1874 – Hawaii signs a treaty with the United States granting exclusive trade rights. |
| 30127 | March 18 | Event | 1892 – Former Governor General Lord Stanley pledges to donate a silver challenge cup, later named after him, as an award for the best hockey team in Canada the Stanley Cup. |
| 30128 | March 18 | Event | 1906 – Traian Vuia flies a heavier-than-air aircraft for 11 meters at an altitude of one meter. |
| 30129 | March 18 | Event | 1913 – King George I of Greece is assassinated in the recently liberated city of Thessaloniki. |
| 30130 | March 18 | Event | 1915 – World War I: During the Battle of Gallipoli, three battleships are sunk during a failed British and French naval attack on the Dardanelles. |
| 30131 | March 18 | Event | 1921 – The second Peace of Riga is signed between Poland and the Soviet Union. |
| 30132 | March 18 | Event | 1922 – In India, Mohandas Gandhi is sentenced to six years in prison for civil disobedience, of which he serves only two. |
| 30133 | March 18 | Event | 1925 – The Tri-State Tornado hits the Midwestern states of Missouri, Illinois, and Indiana, killing 695 people. |
| 30134 | March 18 | Event | 1937 – The New London School explosion in New London, Texas, kills 300 people, mostly children. |
| 30135 | March 18 | Event | 1937 – Spanish Civil War: Spanish Republican forces defeat the Italians at the Battle of Guadalajara. |
| 30136 | March 18 | Event | 1937 – A human-powered aircraft, Pedaliante, flies 1 kilometre (0.62 mi) outside Milan, Italy. |
| 30137 | March 18 | Event | 1938 – Mexico nationalizes all foreign-owned oil properties within its borders. |
| 30138 | March 18 | Event | 1940 – World War II: Adolf Hitler and Benito Mussolini meet at the Brenner Pass in the Alps and agree to form an alliance against France and the United Kingdom. |
| 30139 | March 18 | Event | 1942 – The War Relocation Authority is established in the United States to take Japanese Americans into custody. |
| 30140 | March 18 | Event | 1944 – The eruption of Mount Vesuvius in Italy kills 26 people and causes thousands to flee their homes. |
| 30141 | March 18 | Event | 1946 – Diplomatic relations between Switzerland and the Soviet Union are established. |
| 30142 | March 18 | Event | 1948 – Soviet consultants leave Yugoslavia in the first sign of the Tito–Stalin split. |
| 30143 | March 18 | Event | 1953 – An earthquake hits western Turkey, killing 265 people. |
| 30144 | March 18 | Event | 1959 – President Dwight D. Eisenhower signs a bill into law allowing for Hawaiian statehood, which would become official on August 21. |
| 30145 | March 18 | Event | 1962 – The Évian Accords end the Algerian War of Independence, which had begun in 1954. |
| 30146 | March 18 | Event | 1965 – Cosmonaut Alexey Leonov, leaving his spacecraft Voskhod 2 for 12 minutes, becomes the first person to walk in space. |
| 30147 | March 18 | Event | 1967 – The supertanker Torrey Canyon runs aground off the Cornish coast. |
| 30148 | March 18 | Event | 1968 – Gold standard: The U.S. Congress repeals the requirement for a gold reserve to back US currency. |
| 30149 | March 18 | Event | 1969 – The United States begins secretly bombing the Sihanouk Trail in Cambodia, used by communist forces to infiltrate South Vietnam. |
| 30150 | March 18 | Event | 1970 – Lon Nol ousts Prince Norodom Sihanouk of Cambodia. |