The Continental Army was the army of the United Colonies representing the Thirteen Colonies and later the United States during the American Revolutionary War. It was formed on June 14, 1775, by a resolution passed by the Second Continental Congress, meeting in Philadelphia after the war's outbreak at the Battles of Lexington and Concord on April 19, 1775. As a result, the U.S. Army Birthday is celebrated on June 14.

The Continental Army was created to coordinate military efforts of the colonies in the war against the British, who sought to maintain control over the American colonies. General George Washington was appointed commander-in-chief of the Continental Army and maintained this position throughout the war.

The Continental Army was supplemented by local militias and volunteer troops that were either loyal to individual states or otherwise independent. Most of the Continental Army was disbanded in 1783 after the Treaty of Paris formally ended the war, except for two detachments retained to guard Fort Pitt and West Point.

The Continental Army consisted of soldiers from all the Thirteen Colonies and, after 1776, from all 13 states. The American Revolutionary War began at the Battles of Lexington and Concord, on April 19, 1775, at a time when the colonial revolutionaries had no standing army. Previously, each colony had relied on Patriot militias, which were made up of part-time citizen-soldiers for local defense, or the raising of temporary provincial troops, as was done during the French and Indian War between 1754 and 1763. As tensions with Great Britain increased in the years leading to the war, colonists began to reform their militias in preparation for the perceived potential conflict. Training of militiamen increased after the passage of the Intolerable Acts in 1774. Colonists such as Richard Henry Lee proposed forming a national militia force, but the First Continental Congress rejected the idea. On April 23, 1775, the Massachusetts Provincial Congress authorized the raising of a colonial army consisting of 26 company regiments. New Hampshire, Rhode Island, and Connecticut soon raised similar but smaller forces.

On June 14, 1775, the Second Continental Congress, meeting in present-day Independence Hall in Philadelphia, voted to establish the Continental Army to provide for the common defense of the colonies, and incorporated patriot forces already in place outside Boston (22,000 troops) and New York (5,000). It also raised the first ten companies of Continental Army troops on a one-year enlistment, including riflemen from the Province of Pennsylvania, Province of Maryland, and Colony of Virginia, which were used as light infantry. The Pennsylvania riflemen became the 1st Continental Regiment in January 1776. On June 15, 1775, Congress unanimously elected George Washington commander-in-chief of the Continental Army. Washington accepted, and departed immediately for Boston, where he led the successful Siege of Boston.

Washington served as the Continental Army's commander-in-chief throughout the Revolutionary War without any compensation except for reimbursement of expenses. As the Continental Congress increasingly adopted the responsibilities and posture of a legislature for a sovereign state, the role of the Continental Army became the subject of considerable debate. Some Americans had a general aversion to maintaining a standing army, but the requirements of the Revolutionary War against the British was seen as requiring the discipline and organization of an organized central military. As a result, the Continental Army evolved throughout the war, routinely reorganizing its units and ultimately seeking and obtaining support from France, which sought to counter British influence in North America.

By the end of 1775, during the first year of the Revolutionary War, the Continental Congress operated as a de facto war government, who had authorized the creation of the Continental Army, the Navy, and Marines. A new flag was needed to represent both the Congress and the United Colonies. It is believed that the Continental Union Flag, representing the soldiers and sailors unified as the armed forces of the United Colonies, was raised by George Washington's army on January 2, 1776, at Prospect Hill in Charlestown (present-day Somerville), near his headquarters at Cambridge, Massachusetts.

The Continental Army's forces included several successive armies or establishments: