March 22 – Britain's House of Commons votes in favor of £1,000,000 of appropriations to expand the British Army and Royal Navy operations in North America. 
March 26 – General Edward Braddock and 1,600 British sailors and soldiers arrive at Alexandria, Virginia on transport ships that have sailed up the Potomac River. Braddock, sent to take command of the British forces against the French in North America, commandeers taverns and private homes to feed and house the troops. 
May 3 – France dispatches 3,600 troops to protect its Canadian colonies in Quebec from a British invasion, dispatching 2,400 to Quebec city and 1,200 to Louisbourg in Nova Scotia, unaware that a squadron of 11 fully armed warships from Britain's Royal Navy had sailed toward Canada on April 27. 
May 19 – General Braddock hosts Iroquois leaders Scaroyady, Kaghswaghtaniunt, and Silver Heels at Fort Cumberland, the British Army base in the colony of Maryland. The three chiefs pledge their alliance with the British during in advance of Braddock's expedition into the Ohio Country. 
May 24 – France completes the construction of Fort Duquesne, its new base to the west of the British colony of Pennsylvania. The British capture the fort during the French and Indian War and rename it Fort Pitt. The site, at the junction of the Allegheny River and the Monongahela River, is now Pittsburgh. 
May 30 – General Braddock's troops begin a difficult trek across the heavily wooded Allegheny Mountains from western Maryland into the Ohio country. 
At the entrance of the Saint Lawrence River, a squadron of Royal Navy ships, under the command of British Admiral Edward Boscawen, intercepts the nine French ships dispatched to save Canada; seven of the nine ships are concealed by fog and are able to reach their destination; another of the transports escapes.
July 25 – The decision to deport the Acadians is made, during meetings of the Nova Scotia Council meeting in Halifax. From September 1755-June 1763, the vast majority of Acadians are deported to one of the following British Colonies in America: Massachusetts, Connecticut, New York, Pennsylvania, Maryland, Virginia, North Carolina, South Carolina and Georgia. Contrary to popular belief, no Acadians are sent to Louisiana. Those sent to Virginia are refused and then sent on to Liverpool, Bristol, Southampton and Penryn in England. In 1758 the Fortress of Louisbourg falls, and all of the civilian population of Isle Royal (Cape Breton Island) and Isle St. Jean (Prince Edward Island) are repatriated to France. Among them were several thousand Acadians, who had escaped the deportation by fleeing into those areas. Very few Acadians successfully escape the deportation, and do so only by fleeing into some of the northern sections of present day New Brunswick. The event inspires Longfellow to write the epic poem Evangeline.
September 16 – Sir Charles Hanbury-Williams, the new British Minister to Russia, secures an alliance signed by Empress Catherine the Great. The Russian Empire agrees to provide up to 55,000 troops to defend the Electorate of Hanover against invasion by Prussia. At the time, King George II of Great Britain is also the ruler of the German duchy; the Russian troops are provided in return for an annual payment of £600,000. 
October 17 – The Mount Katla volcano erupts in Iceland, and continues ejecting ash for the next 120 days, finally ceasing on February 13. An estimated 1.5 cubic kilometers (1.5 billion cubic meters or 53 billion cubic feet) of tephra is discharged by the volcano.
November 1 – More than 40,000 people are killed by the 8.5 magnitude 1755 Lisbon earthquake. The tremor begins at 9:40 in the morning local time off of the Atlantic coast of Portugal and sends a tsunami that strikes the coasts of Portugal, Spain and Morocco.