The Last of Us is a survival horror action adventure game. The story focuses on the two characters Joel and Ellie. The game starts in a contemporary, but post-apocalyptic version of Boston twenty years after the outbreak of the Cordyceps Brain Infection (CBI), an infection spread by a mushroom that turns anyone infected into zombie-like creatures in two days. The opening sequence is set during the outbreak and it has Joel escape the invaded city with the help of his brother Tommy. Twenty years later, civilization is almost entirely destroyed. Independent groups of survivors have organized themselves into military outfits that quarantine zones, hold curfew and distribute rations. Others are part of the resistance group the Fireflies, while Joel is a member of an independent group. Together with his friend Tess, he survives by smuggling goods in and out of the city. During a mission they get into contact with a Fireflies member who offers stolen weapons back if they escort the 14-year-old girl Ellie out of the city. After some events and revelations about Ellie's importance, Joel and Ellie end up together and their journey is documented in the course of a year and a few months, spread over five seasons.
The player controls Joel from a third-person perspective. Ellie can also be controlled by herself for some extensive parts in the later chapters. Similar to the developer's previous Uncharted games, gameplay combines action elements, exploration and puzzle-solving. Joel is however not as strong or acrobatic and he often needs to use ladders, planks and other items to climb and get around. Similarly, the survival horror theme with limited ammo and health makes him very vulnerable to attacks and a stealth approach is often more effective. Enemies include various five types of infected (Runners, Stalkers, Clickers, Bloaters and Spore Cadavers) each with their own characteristics, but also humans from the military groups and other survivors. There is a selection of close and long-ranged guns, along with melee weapons that can be modded, regular fist fighting, and items such as molotov cocktails, smoke bombs and nail bombs. Ammo is very limited and initially the reloading speed and firing rate are slow. Melee weapons can only be used a few times before they break down.
More can be achieved through stealth. Joel is able to duck and sneak around at various speeds, and he can activate a hearing sense that allows him to vaguely see and hear silhouettes through walls based on sounds. By sneaking up on an enemy, it can be taken out through strangling, a quick kill with a shiv or another type of takedown. Certain enemies are blind and only react to sound. As soon as Joel is detected, other enemies are warned and the player has to decide upon confrontation or breaking the line of sight by hiding for some time. During attacks or when being held there are often short quick time events to break free, but for some enemies a single hit is deadly right away. Further possibilities include sprinting, using a flash light in dark areas, and swimming. Joel can pick up bottles or bricks and throw them to distract enemies. Certain enemies can be stun by throwing at them directly. Cover is based on line of sight and is not performed through a separate action. It is achieved automatically by moving behind objections and Joel is not glued to his cover position, as both sound and line of sight entirely determine the cover's effectiveness.
Progress through the story and the environment is entirely linear, but there is some focus on exploration along with small optional areas. The city is almost entirely destroyed and the characters move through the debris and abandoned houses, but there are also parts where nature has taken back the environment and lush scenery outside the city. Next to Boston and the surrounding environment, the characters visit Pittsburgh, Colorado and Salt Lake City eventually. A large part of the exploration is needed to gather items. Various tools and items can be collected to craft them into items such as health kits, shivs, molotov cocktails, (smoke) bombs, modded melee weapons and more. Supply is limited, so the player has to choose between offensive and defensive means. At workbenches gears, bolts and other metals are used to improve the characteristics of weapons such as firing rate, reloading speed, weapon sway and ammo capacity. The full range of upgrades only becomes available when up to five levels of tool skills have been unlocked. Supplement pills collected along the way are used to improve the overall skills influencing maximum health, hearing capacity, crafting speed and more. Abilities can also be upgraded by locating training manuals. Ellie and other AI companions are controlled automatically and can never be detected or hurt by opponents, except for a few specific sequences. There is a lot of focus on conversations along the way, as well as the relationship between the characters. This is also furthered through various cut-scenes, both rendered and in-game.
Multiplayer is called Factions with matches for up to eight players simultaneously. At the beginning the player chooses between the Hunters of Fireflies factions with a custom character. The initial faction selection cannot be reversed until the clan has been defeated or the multiplayer story has been completed. The story consists of a light narrative that frames the various encounters, as the aim is to help a clan grow and survive. Players are organized in clans, but these can also be populated with friends' names through a Facebook connection. While playing various status updates about the members are shown, as they are sent out to fight, locate supplies etc. Multiplayer progresses by one day at a time by playing matches in one of the two game modes: Supply Raid and Survivors. Both are team death match variations, with a finite pool of 20 team respawns in the former and one life per round in the latter. Just like the single-player, the focus is mostly on stealth and gathering supplies to craft. Ammo is also limited and the Listen mode from the single-player is available, but only for a short duration and as a specific perk. Crafted items can be used in-game or can be saved to further the clan's status in the larger frame as supplies act as a currency. Sometimes there are specific objectives such as a set number of kills to have the clan grow. Characters can be customized, there is a perk system with survival skills and an overall experience system, and clans can be populated with AI-controlled characters. Character classes consist of Assault, Sniper, Support and Stealth, and a custom one can also be created.