Rensselaer Polytechnic Institute () (RPI) is a private research university in Troy, New York, with additional campuses in Hartford and Groton, Connecticut. It was established in 1824 by Stephen van Rensselaer and Amos Eaton for the "application of science to the common purposes of life" and is the oldest technological university in the English-speaking world and the Western Hemisphere. Numerous American colleges or departments of applied sciences were modeled after Rensselaer.Built on a hillside, RPI's 265-acre (107 ha) campus overlooks the city of Troy and the Hudson River, and is a blend of traditional and modern architecture. The institute operates an oncampus business incubator and the 1,250-acre (510 ha) Rensselaer Technology Park.RPI is organized into six main schools which contain 37 departments, with emphasis on science and technology. It is classified among "R1: Doctoral Universities: Very High Research Activity" and recognized for its degree programs in engineering, computing, business and management, information technology, the sciences, design, and liberal arts. As of 2017, RPI's faculty and alumni included six members of the National Inventors Hall of Fame, six National Medal of Technology winners, five National Medal of Science winners, eight Fulbright Scholarship recipients, and a Nobel Prize winner in Physics; in addition, 86 faculty or alumni are members of the National Academy of Engineering, 17 of the National Academy of Sciences, 25 of the American Academy of Arts and Sciences, eight of the National Academy of Medicine, one of the National Academy of Public Administration, and nine of the National Academy of Inventors. RPI has been ranked since 1970 among the top 50 American universities.

Theta Xi (ΘΞ) is a North American Greek-letter social college fraternity. It was founded at Rensselaer Polytechnic Institute (RPI) on April 29, 1864. Of all the social fraternities today, Theta Xi was the only one founded during the Civil War. Its Grand Lodge is headquartered in suburban St. Louis, Missouri. Since its inception, Theta Xi has grown to include more than 60,000 initiated members. Currently, there are approximately 50 active chapters, and 3 colonies. The Theta Xi Fraternity Chapter House at Rensselaer Polytechnic Institute is listed on the National Register of Historic Places.