Educational Testing Service (ETS) is a U.S.-registered 501(c)(3) non-profit organization. In 1947, the American Council on Education (ACE), the Carnegie Foundation for the Advancement of Teaching, and the College Entrance Examination Board contributed their testing programs, a portion of their assets, and key employees to found Educational Testing Service under the leadership of Henry Chauncey. ETS was formed to take over the testing activities of its founders (whose organizations were not well suited to running operational assessment programs), and to pursue research intended to advance educational measurement and education. Among other things, ACE gave to the new organization the Cooperative Test Service and the National Teachers Examination; Carnegie gave the GRE; and the College Board turned over to ETS the operation (but not ownership) of the SAT.
In creating the organization, the founders of Educational Testing Service brought to life a concept that had been proposed a decade earlier by James Bryant Conant, the President of Harvard University. Conant, who introduced aptitude tests into the undergraduate admissions system, believed that a single organization devoted to educational assessment and research could contribute significantly to the progress of education in the United States.

Today ETS is the world's largest private, nonprofit educational measurement and research organization. The mission of ETS is to advance quality and equity in education for all people worldwide by providing fair and valid assessments, research, and related services. ETS helps teachers teach, students learn, and parents measure the educational and intellectual progress of their children.

ETS develops, administers, and scores more than 50 million tests each year at over 9,000 locations in the U.S. and more than 180 other countries. About 25% of the work carried out by ETS is contracted by the College Board, a private, nonprofit membership association of universities, colleges, school districts, and secondary schools. The most popular of the College Board's tests is the SAT (Scholastic Aptitude Test; for undergraduate school admissions), taken by more than 3 million students annually. ETS also develops and administers the College Board's Preliminary SAT/National Merit Scholarship Qualifying Test (PSAT/NMSQT) and the Advanced Placement program, which is widely used in U.S. high schools for advanced course credit. Since 1983, ETS has conducted the National Assessment of Educational Progress (NAEP), known as the "Nation's Report Card," under contract to the US National Center for Education Statistics. NAEP is the only nationally representative and continuing assessment of what US students know and can do. ETS is currently responsible for coordination among the nine NAEP Alliance contractors, for item development, and for design, data analysis, and reporting. In addition to the contract work that ETS undertakes for nonprofit and government entities like the College Board, the National Center for Education Statistics, and state education departments, the organization offers its own tests. These tests include the Graduate Record Examinations (GRE) (for graduate and professional school admissions), the Test of English as a Foreign Language (TOEFL) (for post-secondary admissions), the Test of English for International Communication (TOEIC) (for use by business and industry), and the Praxis Series (for teacher licensure and certification).

The international campus-like headquarters of ETS is in Princeton Township, New Jersey (with a Princeton, New Jersey, mailing address); processing, shipping, customer service and test security is in nearby Ewing, New Jersey. ETS also has a major office in San Antonio, TX, which houses its K-12 Assessment Programs division, and smaller offices in Philadelphia, PA, Washington, DC, Hato Rey, PR, and Concord, Sacramento, and Monterey, CA. Overseas office locations, all of which are associated with for-profit subsidiaries that are wholly owned by ETS, include Amsterdam (ETS Global BV headquarters), London (ETS Global BV), Seoul (ETS Global BV), Paris (ETS Global BV), Amman (ETS Global BV), Warsaw (ETS Global BV), Beijing (ETS China), and Kingston, Ontario (ETS Canada).

To help support its nonprofit educational mission, ETS, like many other nonprofits, conducts business activities that are unrelated to that mission (e.g., employment testing). Under US tax law, these activities may be conducted (within limits) by the nonprofit itself, or by for-profit subsidiaries. Most of the "off-mission" work conducted by ETS is carried out by such wholly owned, for-profit subsidiaries as Prometric, which delivers tests for hundreds of third-party clients, ETS Global BV, which contains much of the international operations of the company, ETS China, and ETS Canada. Prometric was acquired by ETS in 2007. It operates a test center network composed of over 10,000 sites in 160 countries. Prometric's corporate headquarters are located in Canton (Baltimore, Maryland) in the United States.

ETS operates on an annual budget exceeding U.S. $1 billion. The total revenues of ETS constituted around U.S. $550 million in 2000, around U.S. $800 million in 2005, U.S. $960 million in 2010, and around $1,350 million in 2016, according to financial information reported to the Internal Revenue Service on Form 990, which is publicly available.

More than 3,200 employees work at ETS's offices throughout the United States and the world. More than 2,300 of ETS's professional staff have training and expertise in education, psychology, statistics, psychometrics, computer science, sociology, and the humanities. Of these, around 1,000 have advanced degrees, and 390 hold doctorates. In addition, 1,150 employees support ETS's wholly owned subsidiary Prometric.

ETS is governed by a 16-member Board of Trustees. The board members represent various levels and areas of interest in education and business. Among other things, they select the president of ETS, oversee the leadership provided by ETS officers, set policy, and determine future directions for the entire organization.

By building on existing capabilities, ETS is increasing its presence in certain education markets (K-12, occupational testing and training, and the international arena - Europe, Asia, and Latin America), allowing the organization to offer a broader array of assessments, ones that focus on placement, instruction, and adherence to standards-in addition to those that focus on selection and licensing.

Although ETS is the world's largest testing organization, there are competitors for most of the testing programs and related products and services it develops.

Headquartered in Amsterdam, the Netherlands, ETS Europe makes the world-class products, services, and resources of ETS more readily accessible to European educators and test takers.

ETS has recently been subject to criticism. Americans for Educational Testing Reform (AETR) claims that ETS is violating its non-profit status through excessive profits, executive compensation, and governing board member pay (which the IRS specifically advises against). AETR further claims that ETS is acting unethically by selling test preparation materials, directly lobbying legislators and government officials, and refusing to acknowledge test-taker rights. It also criticises ETS for forcing test-takers to participate in research experiments during the actual exam.