The Battle of Thomas Creek, also known as the Thomas Creek Massacre, was an ambush of a small detachment of mounted Georgia Militia by a mixed force of British soldiers, Loyalist militia, and British-allied Indians on May 17, 1777 near the mouth of Thomas Creek in northern East Florida. The encounter was the only major engagement in the second of three failed attempts by American forces to invade East Florida in the early years of the American Revolutionary War. Col. John Baker led a force of Continental troops and Georgia militia into East Florida. Loyalist, British regulars, and allied Native Americans, under the command of Col. Thomas Brown, prepared for the Continental attack by setting up an ambush. At about 9:00 am on May 17, 1777, Brown’s forces unleashed a volley of musket fire on Baker’s force. Most of the Americans retreated back along their route or into the surrounding swamps. This battle involved the land forces of a two pronged continental attack with the goal of taking St. Augustine from the British. The British and their Native American allies laid a successful trap at Thomas Creek that forced the Continental Army to return to Georgia. Following a raiding expedition by Loyalist Thomas Brown in February 1777 against his state, Georgia President Button Gwinnett organized an expedition against the capital of British East Florida, St. Augustine.

Brown's Indians and rangers set up an ambush ahead of Baker's route, while Prevost's regulars advanced in three columns behind Baker. When Baker's column reached the ambush around 9:00 am, Brown's men delivered a surprise volley at 50 yards from the front and flank. Baker and his men turned to flee, directly into Prevost's oncoming regulars. The Patriots, already shaken, were quickly overwhelmed by the large numbers of rangers and Indians appearing in the underbrush. About half of the Georgians fled at first sight of the enemy; Baker, his horse taken by one of his companions, escaped into the swamps. Governor of East Florida Patrick Tonyn was alerted to the Georgia plans in April, and reported that Baker's company had crossed the St. Marys River on May 10. A mixed band of Loyalist rangers and primarily Muscogee Indians led by Lieutenant Colonel Brown continued to be active on the border between the two provinces after the February raid; they discovered Baker's camp. Three men who escaped captivity arrived two days later, reporting that five of their compatriots had been slain in cold blood by their Indian guards. Given this news, the threat of Tonyn's small fleet, and the fact that his boats were unable to negotiate the narrow channel between Amelia Island and the mainland, Elbert decided to abandon his invasion, and sailed for Savannah on May 26.