Mentor Graphics was founded in 1981 by Tom Bruggere, Gerry Langeler and Dave Moffenbeier. The first round of money, worth $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 an additional $7 million.
Apollo Computer workstations were chosen as the initial hardware platform. Based in Chelmsford, Massachusetts, 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.
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.
In February 2011, activist investor Carl Icahn offered to buy the company for about $1.86 billion in cash.
In 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 started to operate as "Mentor, a Siemens Business". Under the terms of the acquisition, Mentor Graphics kept its headquarters in Wilsonville with workforce intact, and operated as an independent subsidiary.
In January 2021, Mentor became a division of Siemens and was renamed as Siemens EDA.
Mentor product development was located in the US, Taiwan, Egypt, Poland, Hungary, Japan, France, Canada, Pakistan, UK, Armenia, India and Russia.
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 was the company's chief executive officer and president following the acquisition by Siemens, until November 2018 when he became CEO Emeritus. Tony Hemmelgarn is now the president and CEO of Siemens Digital Industries Software, which includes the former Mentor product line.
During the 2022 Russian invasion of Ukraine, Mentor Graphics refused to join the international community and withdraw from the Russian market. Research from Yale University updated on April 28, 2022 identifying how companies were reacting to Russia's invasion identified Mentor Graphics in the worst category of "Digging In", meaning Defying Demands for Exit: companies defying demands for exit/reduction of activities. 
Entrance to company headquarters
Mentor offered the following tools:
Electronic Design AutomationEdit
Integrated circuit layout full-custom and schematic-driven layout (SDL) tools such as IC Station or Memory Builder, a first industry tool for rapid embedded memory design that helped to develop single- or dual-port RAMs (synchronous and asynchronous), as well as diffusion and metal read only memories (ROM)
Nucleus implementation of the Microsoft Point-to-Point Encryption (MPPE) protocol
Nucleus PPP software
Precision Synthesis - Advanced RTL & physical synthesis for FPGAs
Electrical Systems, Cabling, and HarnessEdit
Capital - a suite of integrated tools for the design, validation and manufacture of electrical systems and harnesses
VeSys - a mid-market toolset for vehicle electrical system and harness design
ModelSim is a hardware simulation and debug environment primarily targeted at smaller ASIC and FPGA design
QuestaSim is a simulator with advanced debug capabilities targeted at complex FPGA's and SoC's. QuestaSim can be used by users who have experience with ModelSim as it shares most of the common debug features and capabilities. One of the main differences between QuestaSim and Modelsim (besides performance/capacity) is that QuestaSim is the simulation engine for the Questa Platform which includes integration of Verification Management, Formal based technologies, Questa Verification IP, Low Power Simulation and Accelerated Coverage Closure technologies. QuestaSim natively supports SystemVerilog for Testbench, UPF, UCIS, OVM/UVM where ModelSim does not.
Simcenter Flotherm XT is an electronics cooling CFD tool incorporating a solid modeler for manipulating MCAD parts.
Simcenter FLOEFD is a ‘design concurrent’ CFD tool for use in early-stage product design and is embedded within MCAD systems such as Solidworks, Creo Elements/Pro, CATIA V5 and Siemens NX
Thermal Characterization and Thermal Interface Material (TIM) Measurement equipment:
Simcenter T3STER is a hardware product that embodies an implementation of the JEDEC JESD51-1 standard for IC package thermal characterization and is compliant with JESD51-14 for Rth-JC measurement
Simcenter TERALED provides automation of the CIE 127:2007 standard providing total flux, chromaticity and correlated color temperature (CCT) for power LEDs. With T3Ster it provides thermal resistance metrics for LEDs based on the real dissipated heating power.
Simcenter DYNTIM extends T3Ster, providing a dynamic thermal test station for thermal conductivity measurements of thermal interface materials (TIMs), thermal greases and gap pads.
Simcenter Flomaster is a 1D or system-level CFD solution for analyzing fluid mechanics in complex pipe flow systems (from the acquisition of Flowmaster Ltd in 2012).
CADRA Design Drafting is a 2-1/2D mechanical drafting and documentation package specifically designed for drafting professionals. It provides the tools needed to develop complex drawings quickly and easily (from the acquisition of the CADRA product in 2013).
^"Siemens says Mentor will keep its name, business and HQ". 4 April 2017.