The Battle of Sullivan's Island or the Battle of Fort Sullivan was fought on June 28, 1776, during the American Revolutionary War. It took place near Charleston, South Carolina, during the first British attempt to capture the city from American forces. It is also sometimes referred to as the first siege of Charleston, owing to a more successful British siege in 1780. Sullivan Island was chosen because at the time because it was a geographic obstacle that shielded the harbor. A large vessel sailing into Charleston first had to cross Charleston Bar, a series of submerged sand banks lying about eight miles southeast of the city. Moultrie and his 2nd South Carolina Regiment arrived on the island in March 1776 and began construction of a fortress to defend the island and channel to Charleston Harbor. The construction moved slowly. During late May, British frigates arrived to scout the area and observe the construction of the American fort on Sullivan's Island. The main British fleet arrived outside of Charleston Harbor on June 1. Moultrie observed British scout boat observing possible landing points on nearby Long Island (now called Isle of Palms) just a few hundred yards from Sullivan Island. Lee, the commander of the South Carolina troops, arrived a few days later and was put in command of the American land forces around Charleston.

On the morning of June 28, Fort Sullivan was defended by Colonel Moultrie, commanding the 2nd South Carolina Regiment and a company of the 4th South Carolina Artillery, numbering 435 men. At around 09:00 that morning, a British ship fired a signal gun indicating all was ready for the attack. Less than an hour later, nine warships had sailed into positions facing the fort. Thunder and Friendship anchored about 1.5 miles from the fort while Parker took Active, Bristol, Experiment, and Solebay to a closer position about 400 yards from Sullivan's Island, where they anchored facing broadside to the fort. Each of these ships began to fire upon the fort when it reached its position, and the defenders returned the fire. At one point during the battle, the flag Moultrie had designed and raised over the fort was shot down. The results of the victory were many-fold. For the Americans, it was their first decisive victory. For South Carolina, it produced a confidence in the government led by John Rutledge and forestalled another British effort to take Charleston for over 3 years. More importantly to both South Carolina and the new nation, this daring feat against odds fired the imagination of its citizens. The British did not attempt to renew the battle to try to take the fort again, and by mid-July, the fleet withdrew northward to help the main British army in the campaign against New York. Within days of the battle, the Charlestonians learned of the singing of the Declaration of Independence in Philadelphia which was a sign of their capacity to oppose British arms.