Vermont Republic was the name of what is now the state of Vermont during the 14 years before it joined the United States as the 14th state.
In 1763, the Treaty of Paris ended the French and Indian War, giving the area to the British. Parts of the region were controlled by the Province of New York and Province of New Hampshire. Ethan Allen and his "Green Mountain Boys" fought against the British, then later against these states, and in 1777 Vermont declared itself an independent republic. The area was also called New Connecticut for its first six months of existence, then Vermont, and was sometimes colloquially called the Republic of the Green Mountains. Its history is described in the New Hampshire Grants.
The Constitution of Vermont was drafted and ratified in 1777, and was the first written national constitution in North America. The independent status held until 1791, when Vermont joined the Union, in part as a counterweight to Kentucky. The admission of Vermont was supported by the North, the smaller states, and states concerned about the impact of the sea-to-sea grants held by other states.
Thomas Chittenden was head of Vermont for most of this period, and became its first U.S. governor.