GemStone IV is a multiplayer text-based online role-playing video game (often known as a MUD) produced by Simutronics.

The oldest interface for Windows is called the "Wizard Front End" and offers several useful features such as status readouts, macros, and limited scripting abilities.

A Wizard (similar to the Windows version) also exists for Macintosh Classic, while a Front End named "Avalon" is available for Mac OS X.

GemStone III was promoted on GEnie by promising players the opportunity to receive real-life versions of gems found in-game, something that persisted for many years.

GemStone originally operated with a license to use the Rolemaster game mechanics and Shadow World environment from Iron Crown Enterprises (ICE).

When AOL switched to flat-rate pricing, GemStone did over 1.4 million customer-hours in a single month[7] and was attracting 2,000-2,500 simultaneous players.

Computer Gaming World in 1991 stated that Gemstone III was a good example of the best and worst aspects of online play.

[11] At its peak (1996), GemStone III had over 2,000 simultaneous users and 1 million play hours per month, large numbers for its era.