Family and youth
Bonhoeffer was born in Breslau, Germany (now Wroclaw, Poland) into a middle- to upper-class professional family. He was the sixth of eight children, and he had a twin sister named Sabine. His brother Walter was killed during World War I. His sister was married to Hans von Dohnanyi and was mother of the conductor Christoph von Dohnanyi and a former mayor of Hamburg, Klaus von Dohnanyi. His father, Karl Bonhoeffer, was a prominent German psychiatrist in Berlin; his mother, Paula Bonhoeffer, home-schooled the children.

Though he was initially expected to follow his father into the field of psychology, he decided to become a minister at a very young age. His parents supported his decision and when he was old enough he attended college in Tübingen, received his doctorate in theology from the University of Berlin, and was ordained. He then spent a post-graduate year abroad studying at Union Theological Seminary in New York City. During this time, he would often visit the Abyssinian Baptist Church in Harlem, where he became acquainted with the musical form that ethnomusicologists call the African-American Spiritual. He amassed a substantial collection of recordings of these spirituals, which he took with him back to Germany.

Return to Germany
He returned to Germany in 1931, where he lectured on theology in Berlin and wrote several books. A strong opponent of Nazism, he was involved, together with Martin Niemöller, Karl Barth and others, in setting up the Confessing Church. Between late 1933 and 1935 he served as pastor of two German-speaking Protestant churches in London: St. Paul and Sydenham. He returned to Germany to head an illegal seminary for Confessing Church pastors, first in Finkenwalde and then at the von Blumenthal estate of Gross Schlönwitz, which was closed on the outbreak of war. The Gestapo also banned him from preaching, teaching, and finally speaking at all in public. During this time, Bonhoeffer worked closely with numerous opponents of Adolf Hitler.

During World War II, Bonhoeffer played a key leadership role in the Confessing Church, which opposed the anti-semitic policies of Adolf Hitler. He was among those who called for wider church resistance to Hitler's treatment of the Jews. While the Confessing Church was not large, it represented a major focus of Christian opposition to the Nazi government in Germany.

In 1939 Bonhoeffer joined a hidden group of high-ranking military officers based in the Abwehr, or Military Intelligence Office, who wanted to overthrow the National Socialist regime by killing Hitler. He was arrested in April 1943 after money used to help Jews escape to Switzerland was traced to him, and he was charged with conspiracy. He was imprisoned in Berlin for a year and a half. After the unsuccessful July 20 Plot in 1944, Bonhoeffer's connections to the conspirators were discovered.

He was moved to a series of prisons and concentration camps ending at Flossenbürg. Here, Dietrich Bonhoeffer was executed by hanging at dawn on 9 April 1945, just three weeks before the liberation of the city. Also hanged for their parts in the conspiracy were his brother Klaus and his brothers-in-law Hans von Dohnanyi and Rüdiger Schleicher. For humiliation, and for the sadistic whim of the SS-staff present, all four men were forced to strip down completely in their cells before walking totally naked to the gallows.

Bonhoeffer's legacy
Dietrich Bonhoeffer is considered a martyr for his faith; in the mid-1990s, the German Government officially absolved him of any "crimes" he might have committed pursuant to the positive law of the National Socialist regime. The calendars of the Episcopal Church and the Evangelical Lutheran Church in America commemorate him on April 9, the date on which he was hanged in 1945.

An oft-quoted line from one of his more widely read books, The Cost of Discipleship (1937), foreshadowed his death. "When Christ calls a man, he bids him come and die." His books Ethics (1949) and Letters and Papers from Prison (1953) were published posthumously.

The theological and political reasons behind his shift from Christian pacifism, which he espoused in the mid-1930s, to participation in planning the assassination of Hitler are much debated.

Bonhoeffer's last writings, as found in his fragmentary “Letters and Papers from Prison,” continue to intrigue theologians. In them he introduced the concepts of "religionless Christianity" and “a world come of age,” which in turn became incorporated into both John A.T. Robinson’s controversial 1963 book “Honest to God” and the “Death of God” movement. Bonhoeffer is one of the few theologians embraced by both liberal and conservative Christians, but each group interprets his prison theology differently.

Conservatives see those writings as simply another expression of his earlier traditional theology, although perhaps done in updated language. Liberals interpret his prison writings as a radical new expression of a much more secular understanding of the basic Christian message, and before his death Bonhoeffer himself frequently commented on the radical nature of his late thought. It is universally agreed that, with his death, the world lost a most insightful theological mind.

There are some who feel Liberation theology was first articulated by Bonhoeffer in the late 1930s.

Bonhoeffer is one of the ten 20th-century martyrs from across the world who are depicted in statues above the Great West Door of Westminster Abbey, London.