Assassin's Creed III is an action-adventure, stealth game set in an open world environment and played from a third-person perspective. The main narrative of the game follows Ratonhnaké:ton, also known as Connor, an 18th-century Assassin from Colonial America, and his involvement in various events during the American Revolution and the Revolutionary War. In the game's prologue, consisting of the first three main sequences, players control Connor's father Haytham Kenway, the leader of the Colonial Templars, while in the modern-day sequences, the player character is series protagonist Desmond Miles, who searches for a way to protect the Earth from an upcoming solar flare on December 21, 2012. The game world consists of three main areas: Boston, New York City, and a large wilderness known as the Frontier (which is roughly 1.5 times bigger than Rome in Assassin's Creed: Brotherhood). Portions of the Eastern Seaboard and Caribbean Sea can also be explored during the naval side missions.
Free running has been simplified to allow for more fluid parkour in the cities and wilderness, such as climbing and running on trees, mountains, cliffs, etc. Close combat has also been modified, allowing Connor to dual-wield weapons and take down multiple opponents at once and players no longer need to manage the lock-on mechanic. Aiding this, Connor has access to a wide range of weapons which include muskets, swords, pistols, native weapons such as the tomahawk and bow and arrow, the Rope Dart (used to pull foes or hang them from above) and the Assassins' signature Hidden Blades. Human shields can be used against firing lines of enemies. Medicine is no longer used as health recovers automatically. Stealth is also revamped, allowing players to use natural elements such as tall grass and trees to hide, along with the ability to blend between any two people.
Assassin's Creed III features new weather simulations such as snow, fog, and rain. The seasons can also change i.e., Summer and Winter, which not only affect visuals but also gameplay, as the player will find that they run slower in deep snow. Snowfall can reduce visibility for the player and enemies, aiding stealth. The game also features a wide variety of animals, both domestic (such as horses, cows, and dogs) and wild (deer, wolves, bears, etc.). Wild animals are found in the Frontier and can be hunted for meat or marrow in order to be sold. The quality of the kill determines the price, encouraging the player to hunt silently. For this, traps and bait can also be used.
The economy is now based on the Davenport Homestead, which also acts as Connor's adoptive home. The site can be visited by people such as carpenters, tailors, etc. suffering from displacement due to the war. Helping and interacting with these non-player characters (NPCs) will encourage them to settle in the Homestead. From there on, the player can craft various items and trade with them, and then sell the goods to the cities via caravan. The player can also help them build relationships with each other, which will then result in the formation of a small community.
A revamped version of the recruitment system introduced in Assassin's Creed: Brotherhood returns as players can enlist citizens to the Assassins' cause by completing optional "Liberation" missions. Unlike previous games, the player is limited to only six Assassin recruits, but these recruits are each given distinct personalities and backstories, and have a much larger skill set, allowing them to start riots, provide a cover escort, and set up an ambush, among others. Other side missions include collecting Benjamin Franklin's lost Almanac pages, exploring underground tunnels to unlock fast-travel stations, joining hunting and fighting clubs, investigating various frontiersman rumors like the UFOs and Sasquatches, and "peg-legs" missions in which Connor goes to underground forts and wastelands to uncover the legend of Captain Kidd's treasure. In addition, minigames such as Bowls, Checkers, Fanorona, and Nine men's morris are playable for the first time in the series.
Assassin's Creed III introduced naval gameplay to the series. During the main story, Connor captains a brig, the Aquila, and is given the opportunity to upgrade it with improved weapons and hull armor. Control of the ship relies on environmental factors such as wind direction and speed, local presence of storms, high waves, and rocks. Engagements are by cannon, with broadsides covering both flanks of the ship, swivel guns that can be used to damage smaller ships which can also be boarded to find treasure, and chain shots from the broadsides as well to take down the masts of larger ships and disable them. The Aquila is usable only during a few main story missions and a series of dedicated side missions.