Mentor Graphics, Inc was a US-based multinational corporation dealing in electronic design automation (EDA) for electrical engineering and electronics, and is now a subsidiary of Germany industrial giant Siemens. Founded in 1981, the company is headquartered in Wilsonville, Oregon, and employs roughly 5,200 people worldwide with annual revenues of around $1 billion.

In 1981, the idea of computer-aided design for electronics as the foundation of a company occurred to several groups - those who founded Mentor, Valid Logic Systems, and Daisy Systems. One of the main distinctions between these groups was that the founding engineers of Mentor, whose backgrounds were in software development at Tektronix, ruled out designing and manufacturing proprietary computers to run their software applications. They felt that hardware was going to become a commodity owned by big computer companies, so instead they would select an existing computer system as the hardware platform for the Computer Aided Engineering (CAE) programs they would build.

By February 1981, most of the start-up team had been identified; by March, the three executive founders, Tom Bruggere, Gerry Langeler and Dave Moffenbeier had left Tektronix, and by May the business plan was complete. The first round of money, $1 million, came from Sutter Hill, Greylock, and Venrock Associates. The next round was $2 million from five venture capital firms, and in April 1983 a third round raised $7 million more. Mentor Graphics was one of the first companies to attract venture capital to Oregon.

Apollo Computer workstations were chosen as the initial hardware platform. Based in Chelmsford, Apollo was less than a year old and had only announced itself to the public a few weeks prior to when the founders of Mentor Graphics began their initial meetings.

When Mentor entered the CAE market the company had two technical differentiators: the first was the software - Mentor, Valid, and Daisy each had software with different strengths and weaknesses. The second, was the hardware - Mentor ran all programs on the Apollo workstation, while Daisy and Valid each built their own hardware. By the late 1980s, all EDA companies abandoned proprietary hardware in favor of workstations manufactured by companies such as Apollo and Sun Microsystems.

After a frenzied development, the IDEA 1000 product was introduced at the 1982 Design Automation Conference, though in a suite and not on the floor.

In June 2008, Cadence Design Systems offered to acquire Mentor Graphics in a leveraged buyout. On 15 August 2008, Cadence withdrew this offer quoting an inability to raise the necessary capital and the unwillingness of Mentor Graphics' Board and management to discuss the offer. Mentor acquired Flomerics Group plc for $60 million in cash in October 2008, and in August 2009, Mentor completed the acquisition of silicon manufacturing testing company LogicVision for $13 million in an all-stock deal. Mentor completed the acquisition of Valor Computerized Systems in March 2010 in a cash and stock deal valued at $50 million.

On 22 February 2011, Carl Icahn, an activist investor, made an offer to buy the company for about $1.86 billion in cash.

As of 2012, Mentor's major competitors are: Cadence Design Systems, Synopsys, Altium, and Zuken.

On March 3, 2015 Mentor Graphics announced it had acquired the business assets of Tanner EDA.

On 14 November 2016, Mentor Graphics announced that it was to be acquired by Siemens for $4.5 billion, at $37.25 per share, a 21% premium on Mentor's closing price on the previous Friday. The acquisition was completed in March 2017.

Mentor Graphics product development takes place in the USA, Poland, Hungary, Japan, Pakistan, India and Egypt. James "Jim" Ready, left Mentor in 1999 to form the embedded Linux company MontaVista. Neil Henderson joined Mentor Graphics in 2002 with the acquisition of Accelerated Technology Inc. Stephen Mellor, a leader in the UML space and co-originator of the Shlaer-Mellor design methodology, joined Mentor Graphics in 2004 following the acquisition of Project Technology.

Walden C. Rhines is the company's chairman of the board and chief executive officer whereas Gregory K. Hinckley serves as the president of the corporation.

Mentor Graphics distributes the following tools:

The Veloce product family enables SoC emulation and transaction-based acceleration.