Wilhelm Adalbert Hosenfeld (German pronunciation: [ˈvɪl(hɛl)m ˈhoːzənfɛlt]; 2 May 1895 – 13 August 1952) was a German Catholic school teacher, Nazi activist, and propaganda and intelligence officer in the German Army during World War II. He served as the commander of prisoner-of-war camps in the General Government and from 1940 as an intelligence and counterintelligence officer in the garrison of occupied Warsaw. During the Warsaw Uprising, he interrogated captive Polish civilians, Polish resistance members and Red Army soldiers before their execution.

He is credited with rescuing or assisting at least three Polish Jews, including the pianist and classical composer Władysław Szpilman during the German destruction of Warsaw, and with having helped a number of Polish people under Nazi occupation. Hosenfeld's assistance to Szpilman was portrayed in the 2002 film The Pianist. His efforts were recognised by the posthumous award of the Commander's Cross of the Order of Polonia Restituta from the President of Poland Lech Kaczyński in 2007, and of the Righteous Among the Nations title from Yad Vashem in 2009.

Hosenfeld was born into the family of a Roman Catholic schoolmaster living near Fulda in Hesse. He was influenced by the Catholic Action and Church-inspired social work.^{[citation needed]} He fought as an infantry soldier with the Imperial German Army during World War I in Flanders, the Baltics and Romania from 1914 to 1917. Severely wounded in 1917, he received the Iron Cross Second Class. He viewed the Treaty of Versailles as a national humiliation. After returning from the front he married Annemarie Krummacher, who is said to have exerted a pacifist influence on him.^{[citation needed]} He worked as a teacher in Catholic schools during the interwar period; as a "moderniser" he rejected the caning of students.

During the 1920s, he became active in the Wandervogel section of the German Youth Movement and participated in organised sport, both of which led him to enlist in the Sturmabteilung (SA), the original paramilitary wing of the Nazi Party. He joined the NSDAP in 1935, and participated in the 1936 and 1938 Nuremberg rallies. His writings from the time opposed the National Socialist political project to the "barbaric" legacy of the French Revolution and the October Revolution. In 1938, he expressed disquiet over the Nazi attacks on religion. In 1939, he was employed as the head teacher in Thalau [de].

Hosenfeld was deployed to Poland for the entirety of his involvement in World War II. He was mobilised as a sergeant of the reserve on 26 August 1939, but his unit did not leave Fulda at the start of the invasion of Poland on 1 September. In late September, with Poland nearly defeated, he arrived in Pabianice with a company under his orders and was appointed as the commander of the prisoner-of-war camp set up in the former Rudolf Kindler [pl] textile factory (Lager Pabianitz) and the oflag located in the nearby School No. 5 at 65 Zamkowa St, both organised as transit camps for captives taken at the Battle of the Bzura. He oversaw the construction of barbed wire fencing, watch towers and machine gun positions to guard the camp. While stationed in Pabianice, Hosenfeld recorded his "outrage" at the "rough treatment" of Jewish prisoners, and the "relish" of Polish observers. He considered the "terrible rage" of local ethnic Germans against the Poles justified by the presumed "bestial behaviour of the Poles who were irresponsibly incited" against Germans in the lead-up to the war. Hosenfeld permitted the families of inmates to visit them against the camp rules. He intervened to secure the release of several Poles from German custody, befriended their families, and would later lodge his wife with his Polish contacts.

From December 1939, he was stationed in Węgrów, where he remained until his battalion was moved another 30 km away to Jadów at the end of May 1940. He was finally transferred to Warsaw in July 1940, where he spent the rest of the war, for the most part, attached to Wachbataillon (guard battalion) 660, part of the Wach-Regiment Warschau (Warsaw Guard Regiment) in which he served as a staff officer and as the battalion sports officer. As an intelligence officer, he reported to the Stabsabteilung Ic (Feindaufklärung und Abwehr) [de] in the Oberkommando der Wehrmacht. In late August and early September 1940, he acted as a liaison officer for the Wien-Film crew commissioned by the Reich Ministry of Public Enlightenment and Propaganda and helped it choose set locations across the General Government for the making of the anti-Polish propaganda film Homecoming (1941).

He ran the Wehrmacht sports school in Warsaw and was in charge of military sports events at the Polish Army Stadium, renamed the Wehrmacht Stadium. During the deportation and mass murder of Jews from the Warsaw Ghetto (codenamed Grossaktion Warsaw) in the summer of 1942, he organised a week-long sports competition featuring 1,200 military athletes, then left with his wife for a week's leave in Berlin. Following his return, he hid two surviving Jews, among them Leon Warm-Warczyński who had escaped a transport to the Treblinka extermination camp, on the sports school premises. Throughout the Warsaw period, he used his position to protect fugitives from the Gestapo, including at least one anti-Nazi ethnic German, by providing them with documents and jobs at the sports school.

Hosenfeld was promoted to captain of the reserve in 1942. In his diary from this period, he began to draw a moral equivalence between National Socialism and Communism, but expressed his pride in belonging to the "resilient" German nation and argued that the National Socialist idea was a lesser evil compared to losing the war. By the end of 1943, he noted down his hope for a coup within the Third Reich similar to Marshal Pietro Badoglio's takeover in Italy, leading to a separate peace between Germany and the Western Allies.