Wilhelm "Willi" Graf (2 January 1918 – 12 October 1943) was a German member of the White Rose resistance group in Nazi Germany. The Catholic Church in Germany included Graf in their list of martyrs of the 20th century. In 2017, his cause for beatification was opened. He was given the title Servant of God, the first step toward possible sainthood.

Willi Graf was born in Kuchenheim near Euskirchen. In 1922, his family moved to Saarbrücken, where his father ran a wine wholesaler and managed the Johannishof, the second largest banquet hall in the city. Graf attended school at the Ludwigs gymnasium. It was not long before he joined, at the age of eleven, the Bund Neudeutschland, a Catholic youth movement for young men in schools of higher learning, which was banned after Hitler and the Nazis came to power in 1933. In 1934, Graf joined the Grauer Orden ("Grey Order"), another Catholic movement which became known for its anti-Nazi rhetoric. It, too, was banned and for this reason, it formed many splinter youth groups.

Graf showed conviction in his beliefs from a young age. Although compulsory at the time, he refused to associate with the Hitler Youth, even when he was threatened with becoming ineligible to go to University unless he joined the Hitler Youth. While other future members of the White Rose initially embraced the Hitler Youth, Graf never did so. Moreover, in his address book he crossed out the names of friends who had joined the Hitler Youth, refusing to associate with them. In 1935, at the age of 17, Graf and a few friends marched in an annual May Day parade. The parade was dominated by swastikas, brown-shirted Hitler Youth troops marching in formation, and "Sieg Heils." However, Graf and his friends marched under their tattered school flag, making great effort to stand out from their peers. They did not don any swastikas, or participate in any of the "Sieg Heil" salutes.

While his parents never placed much emphasis on literature and written works (the only books the family owned were religious books), Graf was a voracious reader. Serious and intelligently minded, he enjoyed reading Christian works, with one of his favorite Christian authors being Romano Guardini, one of the leading figures of the liturgical revival of the Catholic Church in Germany. He conducted an in-depth study of Christian authors in his teenage years, with a special focus on works by Romano Guardini. He also enjoyed reading poetry, foreign works, and works banned by the Nazis. Throughout his life, books were a lifeline for him: When he was serving on the Eastern Front, he would write to his friends to see if they could send him more books. In the last year of his life alone he read forty books.

After his Abitur in 1937, Graf did his six-month Reichsarbeitsdienst and afterwards began his medical studies at the University of Bonn. In 1938, he was arrested along with other members of the Grauer Orden and charged by a court in Mannheim with illegal youth league activities–the Bünde having been banned–in relation with his unlawful field trips, camping excursions and other meetings with the Grauer Orden. The charges were later dismissed as part of a general amnesty declared to celebrate the Anschluss. The detention had lasted three weeks. His time in jail did not weaken his decision to participate in anti-Nazi activities or organizations.

After his release, Graf was allowed to return to the University of Bonn to continue his medical studies. While there, Graf was required to report for military duty in August 1939. The next month, September 1939, the war officially began. At this time, the University of Bonn was closed for the course of the war. Graf had chosen the University of Bonn because his aunt and uncle lived in Bonn and offered to let him live with them, as well as the fact that many of his friends (including his then girlfriend Marianne Thoeren) went to that university. After it closed, Graf transferred to the Ludwig-Maximilians-Universität München (LMU). He had completed four semesters at the University of Bonn.

In January 1940, Graf was officially drafted as a Sanitätssoldat (medic). After completing preliminary medical training, he was shipped out to France in September 1940. After serving in France for a few months, he was then transferred to a heavy artillery unit in Belgium. In March 1940, he was transferred to the Eastern Front, having medic duties in both Serbia and Poland. While in Poland in June 1941, he saw the Warsaw Ghetto. This experience caused him to write "Terrible!" in his diary entry of 6 June 1941. He might have written more, but unfortunately during this time of upheaval, he was worried what would happen if others read his diary. On 22 June 1941, Germany declared war on Russia. Soon after, Graf was transferred to Russia, where he would stay until he was allowed to return to Munich to continue his studies in April 1942. During these deployments, he saw terrible things that traumatized him and began to destroy his faith in humanity. As he later wrote to a friend while stationed in Russia, "A war has started that I can't compare to anything else, even here in this land that has always been a mystery to us." In his army medic files it was observed that his care of the ill was "exemplary". Dr. Webel, the Chief Medical Officer, said that Graf "showed himself to be an intrepid medic who never thought about his own safety." Graf was granted the Iron Cross, 2nd class with swords, for his actions. In April 1942, Graf was temporarily relieved of duty and sent to the Ludwig-Maximilians-Universität München to continue his studies. While there, he met Hans Scholl and Alexander Schmorell.

Graf met Hans Scholl and Alexander Schmorell soon after transferring back to Munich. He was introduced to them by Christoph Probst, who took part in fencing with Graf. When Scholl met Graf, he remarked, "he is one of us." Around this time, Graf began to take part in discussions with Scholl, Schmorell, Probst, and their friends.