Terry F. Lenzner is a private investigator and chairman of IGI, a company he founded in 1984 as an adjunct to his former law firm. IGI's founding marked the expansion of Lenzner's investigative law practice, begun a decade earlier through his use of an in-house investigative unit at Rogovin, Huge & Lenzner.

Lenzner's clients over the years have included the U.S. Department of State, which hired IGI to establish a multi-national police monitoring force in Haiti and institute a training program for the country's permanent law enforcement personnel; the United Way of America, which sought an international investigation into allegations that included misappropriation of funds and extensive improper expenditures against the publicly funded charity's president and colleagues; and GTE, which asked IGI to investigate its litigation theory that its adversary, the Home Shopping Network, had lost an enormous amount of revenue through mismanagement and self-dealing rather than due to an alleged faulty telephone system purchased by GTE.  In 1989, GTE won the largest commercial libel judgment ever awarded as of that time.

Lenzner began his career as an attorney in the Civil Rights Division of the U.S. Department of Justice, became a federal prosecutor in the Southern District of New York, and eventually gained national recognition as assistant chief counsel to the Senate Watergate Committee.

He has conducted training sessions on complex investigations for the offices of Inspectors General at several federal agencies.

Lenzner graduate Harvard College and Harvard Law School and was a member of its Board of Overseers from 1970-1976.