Thomas Mifflin (January 10, 1744 – January 20, 1800) is an American merchant and politician from Philadelphia, Pennsylvania.

He serves in a variety of roles during and after the American Revolution, several of which qualify him to be counted among the Founding Fathers.

He is the first Governor of Pennsylvania, serving from 1790 to 1799.

Born in Philadelphia, Mifflin becomes a merchant after graduating from the College of Philadelphia.

He joins the Continental Army after serving in the Pennsylvania Provincial Assembly and the Continental Congress.

During the American Revolutionary War, he serves as an aide to General George Washington and as the Continental Army's Quartermaster General, rising to the rank of major general.

Mifflin returns to Congress in 1782 and is elected President of the Continental Congress in 1783.

He serves as Speaker of the Pennsylvania House of Representatives from 1785 to 1787 and as President of the Pennsylvania Supreme Executive Council from 1788 to 1790.

Mifflin is a delegate to the 1787 Philadelphia Convention and signs the United States Constitution.

He presides over the committee that writes Pennsylvania's 1790 constitution and becomes the state's first governor after the ratification of the new state constitution.

Mifflin leaves office as governor in 1799 and dies the following year.