Born in Horncastle, Lincolnshire to actor parents, Thomas Sully came to America when he was nine years old. In Philadelphia, the young Sully exhibited a talent for drawing and began studying with his older brother, who was a miniature painter. When Sully dedicated himself to painting fulltime he was fortunate enough to received the criticism of the painter, Gilbert Stuart. Like Stuart, Sully was interested in depicting his subjects as heroic figures often taking liberties with an array of details in the work. He also favored a classical style and pretty colors. Sully was also heavily influenced by the work of Charles Wilson Peale and Benjamin West.

In 1801 he moved with his brother's family to Virginia. When his brother died, Sully cared for the family and eventually married his brother's widow. In 1808, upon an offer from a patron, Sully moved to Philadelphia. He would remain in Philadelphia, save two years when he painted and studied in England, for the rest of his life.

Throughout his career Sully painted over two thousand portraits, one of his most famous being a portrait of Queen Victoria. He also painted Rebecca Gratz, Andrew Jackson, and Dr. Benjamin Rush among many others. He was also decorated with many artistic honors including, honorary membership in the National Academy of Design and membership in the American Philosophical Society.

While in Philadelphia, Sully taught at the Pennsylvania Academy of the Fine Arts and was a member of its board of directors from 1816-1832. He was undeniably one of the most renowned portrait painters of the 19th century.

Thomas Sully died in Philadelphia in 1872.