Adam Bargielski was born on 7 January 1903 in Kalinowo, in Łomża County, the son of the farmers Franciszek Bargielski and Franciszka née Jankowska. He grew up in a working countryside household where faith was carried in ordinary labour, and from 1915 to 1924 he attended the Tadeusz Kościuszko commercial gymnasium in Łomża. Like many young Poles of the newly restored Republic, he first sought to serve his country with arms, entering the infantry officer cadet school at Ostrów Mazowiecka; but the Lord had another service in mind. On 5 January 1925 he left the cadet school and entered the major seminary of the Diocese of Łomża.
On 24 February 1929 he was ordained a priest by the Bishop of Łomża, Stanisław Kostka Łukomski. In March of that year he was assigned as vicar of the parish of St Adalbert in Poznań, where he served until September. His bishop, recognising his gifts, sent him abroad in October 1929 to study law in France. For a short time he was chaplain to the Polish sisters at Bischwiller, and from November 1929 he studied at the university college for clerics attached to the University of Strasbourg, taking up canon law. He completed his specialised studies in 1931 and returned home to Poland.
There followed eight years of unglamorous, itinerant parish work — the ordinary road on which most sanctity is made. He served at Puchały (1931–1932), Suwałki (1932–1936), Łabno (1936–1937), Kadzidło (1937–1938), Bronowo and Wąsosz (1938), and finally, from 1939, as vicar of the parish of Myszyniec in the Kurpie country. At Myszyniec he threw himself into Catholic Action and above all into work with the young, forming them in the faith at the very hour when a storm was about to break over Poland.
The German invasion of September 1939 brought the systematic hunting of the Polish clergy. On 9 April 1940 the Gestapo arrested the pastor of Myszyniec, the eighty-three-year-old Father Klemens Sawicki, an old man who could not have survived imprisonment. Father Adam did not hide, nor did he protest from a safe distance. He presented himself to the Gestapo and asked to take the old priest's place. The request was granted: Father Sawicki was released, and the young curate was led away in his stead. In the words later carved on his memorial tablet in the basilica of Myszyniec, "No one has greater love than this, that a man lay down his life for his friends" (John 15:13).
He was taken first, in all probability, to the prison at Ostrołęka, then to the German camp at Soldau (Działdowo). On 25 April 1940 he was delivered to Mauthausen-Gusen, and the following month to Dachau, the great burial ground of the Polish priesthood, where he was registered as prisoner number 4860 and later as number 22061, and housed in block 30/3. With the other Polish priests he was forbidden to celebrate Mass, to pray aloud, to recite the breviary, or to keep any religious object. Stripped of everything that made him visibly a priest, he remained one entirely: witnesses recalled that he never ceased to help his fellow prisoners, and that the persecution never disturbed his deep interior peace. His altar had become the hunger, the cold, and the beatings of the camp, and he offered them.
On 8 September 1942, the feast of the Nativity of the Blessed Virgin Mary, a camp guard struck him and threw him to the ground; he died of the injury. The death certificate sent to his family gave a stroke as the cause. His body was burned in the camp crematorium and his ashes scattered in the fields around Dachau, so that he has no grave but the earth of Bavaria and the memory of the Church.
His people did not forget him. In 1984, at the request of the faithful, a memorial tablet was placed in the basilica of Myszyniec, naming him "the substitute victim for his pastor, Father Klemens Sawicki." Pope John Paul II beatified him in Warsaw on 13 June 1999 among the 108 Polish Martyrs of the Second World War, whose common memorial is kept on 12 June; his own feast is celebrated on 8 September, the anniversary of his martyrdom. Since 2005 he has been patron of the county school complex in Myszyniec, where a tablet bears his portrait and the title "educator of youth, martyr," and a street near the church of Myszyniec carries his name.
May Blessed Adam Bargielski, who took another man's chains upon himself, obtain for us the courage to spend ourselves for our neighbour; imitate today his substitutive charity by taking upon yourself, without being asked, one burden that belongs to someone else.
