Stefan Korboński was born in Praszka, Wieluń County, on 2 March 1901. He was the second of five children of a court clerk, Stefan Korboński Senior, and his wife Władysława née von Körner. The Korboński family came from Kalisz Region. Their family estate was located in Koszuty Poduchowne.
After his father’s death in 1910 (Stefan Korboński Senior died after he had fallen into ice-cold water while hunting), his widowed mother moved with the children to Częstochowa where she began running a boarding house to support her family. Stefan started attending a Russian secondary school, where he remained until the outbreak of Great War. The next two years of his life he spent with his brother Stanisław at Koszuty Poduchowne, in their uncle Kazimierz’ estate. In 1917 he moved back to Częstochowa to continue his education, which had been disrupted by the war, but this time in a Polish secondary school named after Henryk Sienkiewicz. On the wall of the school there is now a plaque in memory of Korboński. The upbringing which he received in Częstochowa had a lasting effect on him: Stefan Korboński was a devout Christian believer until the end of his life. He held the Virgin Mary in great veneration, which manifested itself, among others ways, in his article about the Black Madonna of Częstochowa, published in “Catholic Digest” during his exile, or in the pilgrimage made with his wife to Częstochowa in September 1947 to thank God for sparing his life in 1943.
In 1917, as a Boy Scout, Korboński got involved in the Polish Military Organization (Polska Organizacja Wojskowa), underground movement. On 10 November 1918 he participated in the disarming of German soldiers from the Landsturm Bataillion (Mosbach Baon) stationed in Częstochowa. In that same year, at only 17 years of age, he took part in the defence of Lvov and volunteered for service in the 10th Infantry Regiment, fighting back Ukrainians at Gródek Jagielloński and Sambor.His desire to fight for independence was so great that in the years 1918–1921 he escaped from school three times to join the army. During the war with Bolsheviks of 1920, Korboński was declared unfit for frontline duty, so he volunteered for service as a Staff Sergeant in the 229th Reserve Infantry Regiment, formed in Kalisz and associated with the parent 29th Regiment of Kaniów Riflemen. At the beginning of May, 1921, he also fought in the Third Silesian Rising at Pawonkowo and Olesno. Released from active duty towards the end of May 1921, he came back to Częstochowa to take the examinations for his secondary school diploma. That very same year, he was accepted into the Faculty of Law and Economics of the then-newly founded University of Poznań. Being badly off, Stefan had to follow in his father’s footsteps and choose a course of study leading to a degree in law, despite his keen interest in primeval history and archaeology.He tried to look for ancient sites in the neighboring localities and research for documents in the local archives.
In order to pay the tuition fees, he gave private lessons and taught at a secondary school in Pyzdry like his elder brother Stanisław, and worked for the Poznań recruitment office for job seekers in France. Early in his academic career, Korboński showed great community spirit: Early in his academic career, Korboński showed great community spirit: he would set up discussion groups, as well as edit school and community bulletins. As a university student, he got involved in numerous academic initiatives and was elected to sit on the student government. He also participated in sports: he not only played football and set up football teams. Later on, he developed a keen interest in skiing, becoming a member of the Polish Skiing Association. His other passion was the mountains.
On one of his trips to Zakopane, he brought back a portrait painted by Stanisław Ignacy Witkiewicz, known as “Witkacy”. One year before earning a university diploma, Korboński started his three-year-long supervised legal training at a First Instance Court in Poznań. He then continued on to a Regional Court, a Public Prosecutor’s office, and a Court of Appeal. Then, already a judge, he returned to the First Instance Court. He specialized in German law.