Günter Wallraff is a famous German writer and undercover journalist. Wallraff came to prominence thanks to his striking journalistic research methods and several major books on lower class working conditions and tabloid journalism. This style of research is based on what the reporter experiences personally after covertly becoming part of the subgroup under investigation. Wallraff would construct a fictional identity so that he was not recognisable as a journalist. In this way, he created books which denounce what he considers to be social injustices and which try to provide readers with new insights into the way in which society works.

Wallraff was one of the first people in Germany to invoke his constitutional right not to do armed military service. Despite this refusal, Wallraff was obliged to serve time in the Bundeswehr. Wallraff first took up this kind of investigative journalism in 1969 when he published 13 unerwünschte Reportagen ("13 undesired reports") in which he described what he experienced when acting the parts of an alcoholic, a homeless person, and a worker in a chemicals factory.

He travelled to Greece in May 1974 at the time of the Ioannides military dictatorship. While in Syntagma Square, he protested against human right violations. He was arrested and tortured by the police, as he did not carry, on purpose, any papers on him that could identify him as a foreigner. After his identity was revealed, Wallraff was convicted and sentenced to 14 months in jail. He was released in August, after the end of the dictatorship.

In 1977 Wallraff worked for four months as an editor for the tabloid Bild-Zeitung newspaper in Hanover, calling himself "Hans Esser". In his books Der Aufmacher (pun, meaning both "Lead Story" and "the one who opens") and Zeugen der Anklage ("Witnesses for the Prosecution") he portrays his experiences on the editorial staff of the paper and the journalism which he encountered there, which at times displayed contempt for humanity. In 1987 the journalist Hermann L. Gremliza claimed that he, rather than Wallraff, had written parts of Der Aufmacher. The book also formed the basis for the English-language film The Man Inside from 1990, starring Jürgen Prochnow as Wallraff.

Ganz unten ("Lowest of the Low") (1985) documented Wallraff's posing as a Turkish guest worker, and the mistreatment he received in that role at the hands of employers, landlords and the German government. In 1986 he was awarded Laureate of the International Botev Prize. In January 2003, Russia turned away Wallraff and two other Germans, the former labour minister for the CDU Norbert Blüm and Rupert Neudeck, head of the relief organisation Cap Anamur, as they tried to enter the country to work on a human rights article about Chechnya.

In May 2007, Wallraff announced that he had started yet another undercover journalist work, this time at a German call centre. Autumn 2009, he stunted with a controversial undercover story as a black man to expose latent or explicit racism.

Wallraff's investigative methods have led to the creation of the Swedish verb 'wallraffa' meaning "to expose misconduct from the inside by assuming a role". The word is currently included in the dictionary Svenska Akademiens Ordlista.

His book Aus der schönen neuen Welt: Expeditionen ins Landesinnere was published by Topos Books in 2011.