Kolbe's life was strongly influenced by a childhood vision of the Virgin Mary that he later described:
That night, I asked the Mother of God what was to become of me, a Child of Faith. Then she came to me holding two crowns, one white, the other red. She asked me if I was willing to accept either of these crowns. The white one meant that I should persevere in purity, and the red that I should become a martyr. I said that I would accept them both.
In 1910, Kolbe was allowed to enter the novitiate, where he was given the religious name Maximilian. He professed his first vows in 1911, and final vows in 1914, in Rome, adopting the additional name of Maria, to show his devotion to the Blessed Virgin Mary. Kolbe would later sing hymns to the Virgin Mary in the concentration camp.
Kolbe was sent to Kraków in 1912, and later that same year to the house of studies of the Order in Rome, where he studied philosophy, theology, mathematics and physics. He earned a doctorate in philosophy in 1915 at the Pontifical Gregorian University, and a doctorate in theology in 1919 at the Pontifical University of St. Bonaventure. During his time as a student, he witnessed vehement demonstrations against Popes St. Pius X and Benedict XV in Rome during an anniversary celebration by the Freemasons. According to Kolbe,
They placed the black standard of the "Giordano Brunisti" under the windows of the Vatican. On this standard the archangel, St. Michael, was depicted lying under the feet of the triumphant Lucifer. At the same time, countless pamphlets were distributed to the people in which the Holy Father (i.e., the Pope) was attacked shamefully.
This event inspired Kolbe to organize the Militia Immaculata, or Army of Mary, to work for conversion of sinners and enemies of the Catholic Church, specifically the Freemasons, through the intercession of the Virgin Mary. So serious was Kolbe about this goal that he added to the Miraculous Medal prayer:
Oh Mary, conceived without sin, pray for us who have recourse to thee. And for all those who do not have recourse to thee; especially the Masons and all those recommended to thee.
In 1918, Kolbe was ordained a priest. In 1919, he returned to the newly independent Poland, where he was very active in promoting the veneration of the Immaculate Virgin Mary, founding and supervising the monastery of Niepokalanów near Warsaw, a seminary, a radio station, and several other organizations and publications. Kolbe founded the monthly periodical Rycerz Niepokalanej in 1922, and in 1927 founded a Conventual Franciscan monastery at Niepokalanow, which became a major publishing centre. Kolbe left Poland for Japan in 1930, spending six years there. The monastery at Niepokalanow began in his absence to publish the daily newspaper, Mały Dziennik, which became Poland's top-seller.
Between 1930 and 1936, Kolbe undertook a series of missions to Japan, where he founded a monastery at the outskirts of Nagasaki, a Japanese paper, and a seminary. The monastery he founded remains prominent in the Roman Catholic Church in Japan. Kolbe decided to build the monastery on a mountainside that, according to Shinto beliefs, was not the side best suited to be in harmony with nature. When the atomic bomb was dropped on Nagasaki, Kolbe's monastery was saved because the other side of the mountain took the main force of the blast
On 17 February 1941, he was arrested by the German Gestapo and imprisoned in the Pawiak prison. On 28 May, he was transferred to Auschwitz as prisoner #16670. At the end of July 1941, three prisoners disappeared from the camp, prompting SS-Hauptsturmführer Karl Fritzsch, the deputy camp commander, to pick 10 men to be starved to death in an underground bunker in order to deter further escape attempts. When one of the selected men, Franciszek Gajowniczek, cried out, "My wife! My children!", Kolbe volunteered to take his place.
In his prison cell, Kolbe celebrated Mass each day and sang hymns with the prisoners. He led the other condemned men in song and prayer and encouraged them by telling them they would soon be with Mary in Heaven. Each time the guards checked on him, he was standing or kneeling in the middle of the cell and looking calmly at those who entered. After two weeks of dehydration and starvation, only Kolbe remained alive. The guards wanted the bunker emptied and they gave Kolbe a lethal injection of carbolic acid. Some who were present at the injection say that he raised his left arm and calmly waited for the injection. His remains were cremated on 15 August, the feast day of the Assumption of Mary.
Kolbe was beatified as a Confessor of the Faith by Pope Paul VI in 1971 and canonized by Pope John Paul II on 10 October 1982, with Franciszek Gajowniczek in attendance.