Silicon Graphics, Inc. (stylized as SiliconGraphics before 1999, later rebranded SGI, historically known as Silicon Graphics Computer Systems or SGCS) was an American high-performance computing manufacturer, producing computer hardware and software. Founded in Mountain View, California, in November 1981 by James Clark, its initial market was 3D graphics computer workstations, but its products, strategies and market positions developed significantly over time.

Early systems were based on the Geometry Engine that Clark and Marc Hannah had developed at Stanford University, and were derived from Clark's broader background in computer graphics. The Geometry Engine was the first very-large-scale integration (VLSI) implementation of a geometry pipeline, specialized hardware that accelerated the "inner-loop" geometric computations needed to display three-dimensional images. For much of its history, the company focused on 3D imaging and was a major supplier of both hardware and software in this market.

Silicon Graphics reincorporated as a Delaware corporation in January 1990. Through the mid to late-1990s, the rapidly improving performance of commodity Wintel machines began to erode SGI's stronghold in the 3D market. The porting of Maya to other platforms was a major event in this process. SGI made several attempts to address this, including a disastrous move from their existing MIPS platforms to the Intel Itanium, as well as introducing their own Linux-based Intel IA-32 based workstations and servers that failed in the market. In the mid-2000s the company repositioned itself as a supercomputer vendor, a move that also failed.

On April 1, 2009, SGI filed for Chapter 11 bankruptcy protection and announced that it would sell substantially all of its assets to Rackable Systems, a deal finalized on May 11, 2009, with Rackable assuming the name Silicon Graphics International. The remnants of Silicon Graphics, Inc. became Graphics Properties Holdings, Inc.