Interactive fiction, often abbreviated IF, describes software simulating environments in which players use text commands to control characters and influence the environment. Works in this form can be understood as literary narratives and as video games. In common usage, the term refers to text adventures, a type of adventure game where the entire interface is text only. The term is sometimes used to encompass the entirety of the medium, but is also sometimes used to distinguish games produced by the interactive fiction community from those created by games companies. It can also be used to distinguish the more modern style of such works, focusing on narrative and not necessarily falling into the adventure game genre at all, from the more traditional focus on puzzles. More expansive definitions of interactive fiction may refer to all adventure games, including wholly graphical adventures such as Myst.

As a commercial product, interactive fiction reached its peak in popularity in the 1980s, as a dominant software product marketed for home computers. Because their text-only nature sidestepped the problem of writing for the widely divergent graphics architectures of the day, interactive fiction games were easily ported across all the popular platforms, even those such as CP/M not known for gaming or strong graphics capabilities. Today, interactive fiction no longer appears to be commercially viable, but a steady stream of new works is produced by an online interactive fiction community, using freely available development systems. Most of these games can be downloaded for free from the Interactive Fiction Archive (see external links).

The term "interactive fiction" is also occasionally used to refer to addventure games, which are also called hypertext fiction, collaborative fiction, or even a participatory novels, according to the New York Times. It is also used to refer to literary works that are not read in a linear fashion, but rather the reader is given choices at different points in the text; the reader's choice determines the flow and outcome of the story. The most famous example of this form of interactive fiction is the Choose Your Own Adventure book series. For others, see gamebooks.
Text adventures are one of the oldest types of computer games and form a subset of the adventure genre. The player uses text input to control the game, and the game state is relayed to the player via text output.

Input is usually provided by the player in the form of simple sentences such as "get key" or "go east", which are interpreted by a text parser. Parsers may vary in sophistication; the first text adventure parsers could only handle two-word sentences in the form of verb-noun pairs. Later parsers, such as those built on Infocom's ZIL (Zork Implementation Language), could understand complete sentences. Later parsers could handle increasing levels of complexity parsing sentences such as "open the red box with the green key then go north". This level of complexity is the standard for works of interactive fiction today.

Despite their lack of graphics, text adventures include a physical dimension where players move between rooms. Many text adventure games boasted their total number of rooms to indicate how much gameplay they offered. These games are unique in that they may create an illogical space, where going north from area A takes you to area B, but going south from area B did not take you back to area A. This can create mazes that do not behave as players expect, and thus players must maintain their own map. These illogical spaces are much more rare in today's era of 3D gaming, and the Interactive Fiction community in general decries the use of mazes entirely, claiming that mazes have become arbitrary 'puzzles for the sake of puzzles' and that they can, in the hands of inexperienced programmers, become immensely frustrating for players to navigate.

Interactive fiction shares much in common with Multi-User Dungeons ('MUDs'). MUDs, which became popular in the mid-1980s, rely on a textual exchange and accept similar commands from players as do works of IF; however, since interactive fiction is single player, and MUDs, by definition, have multiple players, they differ enormously in gameplay styles. MUDs often focus gameplay on activities that involve communities of players, simulated political systems, in-game trading, and other gameplay mechanics that aren't possible in a single player environment.

Interactive fiction usually relies on reading from a screen and on typing input, although text-to-speech synthesizers allow blind and visually impaired users to play interactive fiction titles as audio games.