Sir Tejinder Singh Virdee, FRS (Punjabi: ਤਜਿੰਦਰ ਸਿੰਘ ਵਿਰਦੀ, born 13 October 1952), is a Kenyan-born British experimental particle physicist and Professor of Physics at Imperial College London. He is best known for originating the concept of the Compact Muon Solenoid (CMS) with a few other colleagues and has been referred to as one of the 'founding fathers'  of the project. CMS is a world-wide collaboration which started in 1991 and now has over 3500 participants from 45 countries.
 Virdee was elected Fellow of the Royal Society and of the Institute of Physics (IOP) in 2012. In recognition of his work on CMS he has been awarded the IOP High Energy Particle Physics group prize (2007) and the IOP Chadwick Medal and Prize (2009). In 2012, he was awarded the 2013 Special Breakthrough Prize in Fundamental Physics
for 'leadership in the scientific endeavour that led to the discovery of the new Higgs-like particle by the ATLAS and CMS collaborations at CERN's Large Hadron Collider (LHC) along with 6 other physicists. He was awarded the 2013 European Physical Society High Energy and Particle Physics Prize and the 2017 American Physical Society Panofsky Prize for his pioneering work and outstanding leadership in the making of the CMS experiment. In 2020 he was awarded the Blaise Pascal Medal of the European Academy of Sciences in Physics. He was also on the Physical Sciences jury for the Infosys Prize in 2020.
 In 2014, Virdee was knighted in the Queen's Birthday Honours list for services to science.
 Tejinder Virdee was born in 1952 to Sikh parents Udham Kaur and Chain Singh Virdee in Nyeri, Kenya. Virdee went to school in Kisumu at the Kisumu Boys High School. Due to the prevailing circumstances in Kenya at the time, his family (of Indian Sikh origin) emigrated in 1967 to Birmingham, England. He credits part of his interest in physics to Howard Stockley, his physics teacher at King's Norton Boys' School, Birmingham, whom he describes as an 'inspirational teacher'. He also remembers visiting Birmingham Museum of Science and Industry, where he stumbled across a cloud chamber sparking his interest in the study of the structure of matter. Virdee obtained a B.Sc. in Physics from Queen Mary College, University of London in 1974.
 After completing his Ph.D. at Imperial College London, on an experiment conducted at the Stanford Linear Accelerator Center (SLAC) in California, he joined CERN in 1979 as a Fellow of the Experimental Physics Division. Virdee’s early scientific career (1979-1984) involved verifying the strange notion that the “quarks” (the constituents of the protons the neutrons and all other hadrons) carry fractional electric charge. This was successfully demonstrated by the NA14 photoproduction experiment at CERN in the mid-eighties. Following NA14 he joined the UA1 experiment at CERN's proton-antiproton collider (SPS) where his interest in high-performance calorimetry was developed, leading to his invention of a novel technique of collecting light in plastic scintillator-based calorimeters.
 Towards the end of UA1, (1990) Virdee, with a few other colleagues, started planning an experiment based on a high field solenoid that would be able to identify the missing elements of the Standard Model (SM) and also to probe in full the physics of the TeV scale. This was to become the CMS experiment at the LHC, one of the most complex instruments science has ever seen. Since 1991 Virdee has played a crucial role in all phases of CMS. Over the last two decades this has covered conceptual design, intensive R&D, prototyping, construction, installation, commissioning, data-taking and finally physics exploitation. He has been the driving force behind many of the major technology decisions made in CMS, especially the selection of the calorimeter technologies. The CMS hadron calorimeter uses the technique he had invented earlier.
 The possibility of discovering a Higgs-like boson played a crucial role in the conceptual design of CMS,  and served as a benchmark to test the performance of the experiment. In 1990 Virdee and a colleague, Christopher Seez, carried out the first detailed simulation studies of the most plausible way to detect the SM Higgs boson in the low-mass region in the environment of the LHC: via its decay into two photons. Understanding that dense scintillating crystals offer arguably the best possibility of achieving excellent energy resolution, Virdee made a compelling case for the use of lead tungstate scintillating crystals (PbWO4) for the electromagnetic calorimeter of CMS and then led the team that proved the viability of this technique, a technique that has played a crucial role in the discovery of the new heavy boson, in July 2012. Virdee was deeply involved in this search for the Higgs boson, especially via its two-photon decay mode.
 Virdee was the deputy project leader of CMS between 1993 and 2006 and was then elected project leader (Spokesperson) in January 2007 for a period of three years. He oversaw the final stages of construction, installation and data taking with the first collisions at the LHC.
 Virdee is a major voice in arguing for the long-term future of the LHC accelerator and its experiments. An increase in the interaction rate by almost a factor of around ten is being advocated for the CMS and ATLAS experiments. To benefit fully from this luminosity increase the CMS detector will be upgraded. Virdee is leading efforts to replace the detector's endcaps with a novel silicon-based technology that measures the energy and momentum of particles to unprecedented levels of precision.
 Beyond his contributions to particle physics he is a promoter of science and education, especially in Africa. He funds science-related education activities in schools and universities in Africa, India and the United Kingdom.
 Virdee has given several keynote speeches at international conferences, opening or closing addresses at particle physics conferences and public lectures on the LHC Project.
These include the 2007 Schrödinger Lecture, the 2012 Peter Lindsay Lectures at Imperial College, the 16th Kaczmarczik Lecture at Drexel University, Philadelphia in 2011, the Keynote Speech at the 2009 Intel International Science and Engineering Fair, Reno, USA and joint lectures on the LHC Project with Prof. Edward Witten in Philadelphia, U.S.A. (2008) and Split, Croatia (2009).
 Amongst his interviews are a dialogue with A. C. Grayling, and an interview with Jim Al-Khalili on the BBC Radio 4 programme “The Life Scientific”.
 Virdee plans to use the money to support science in schools in Sub-Saharan Africa—see Peter Woit (12 June 2013). "Nature on the new Nobels". Not Even Wrong. Retrieved 22 June 2013.