Jehovah's Witnesses endured intense persecution under the Nazi regime. Actions against the religious group and its individual members spanned the Nazi years 1933 to 1945. Unlike Jews and Sinti and Roma ("Gypsies"), persecuted and killed by virtue of their birth, Jehovah's Witnesses had the opportunity to escape persecution and personal harm by renouncing their religious beliefs. The courage the vast majority displayed in refusing to do so, in the face of torture, maltreatment in concentration camps, and sometimes execution, won them the respect of many contemporaries.

Founded in the United States in the 1870s, the Jehovah's Witnesses organization sent missionaries to Germany to seek converts in the 1890s. By the early 1930s, only 20,000 (of a total population of 65 million) Germans were Jehovah's Witnesses, usually known at the time as "International Bible Students."

Even before 1933, despite their small numbers, door-to-door preaching and the identification of Jehovah's Witnesses as heretics by the mainstream Protestant and Catholic churches made them few friends. Individual German states and local authorities periodically sought to limit the group's proselytizing activities with charges of illegal peddling. There were also outright bans on Jehovah's Witnesses' religious literature, which included the booklets The Watch Tower and The Golden Age. The courts, by contrast, often ruled in favor of the religious minority. Meanwhile, in the early 1930s, Nazi brownshirted storm troopers, acting outside the law, broke up Bible study meetings and beat up, individual Witnesses.

After the Nazis came to power, persecution of Jehovah's Witnesses intensified . Small as the movement was, it offered, in scholar Christine King's words, a "rival ideology" and "rival center of loyalty" to the Nazi movement. Although honest and as law–abiding as their religious beliefs allowed, Jehovah's Witnesses saw themselves as citizens of Jehovah's Kingdom; they refused to swear allegiance to any worldly government. They were not pacifists, but as soldiers in Jehovah's army, they would not bear arms for any nation.

Jehovah's Witnesses, in Germany as in the United States, had refused to fight in World War I. This stance contributed to hostility against them in a Germany still wounded by defeat in that war and fervently nationalistic, attempting to reclaim its previous world stature. In Nazi Germany, Jehovah's Witnesses refused to raise their arms in the "Heil, Hitler!" salute; they did not vote in elections; they would not join the army or the German Labor Front (a Nazi affiliate, which all salaried employees were required to join after 1934).

Jehovah's Witnesses were denounced for their international and American ties, the apparent revolutionary tone of their millennialism (belief in the peaceful 1,000 year heavenly rule over the earth by Christ, preceded by the battle of Armageddon), and their supposed connections to Judaism, including a reliance on parts of the Bible embodying Jewish scripture (the Christian "Old Testament"). Many of these charges were brought against more than 40 other banned religious groups, but none of these were persecuted to the same degree. The crucial difference was, the intensity Witnesses demonstrated in refusing to give ultimate loyalty or obedience to the state.

In April 1933, four months after Hitler became chancellor, Jehovah's Witnesses were banned in Bavaria and by the summer in most of Germany. Twice during 1933, police occupied the Witnesses' offices and their printing site in Magdeburg and confiscated religious literature. Witnesses defied Nazi prohibitions by continuing to meet and distribute their literature, often covertly. Copies were made from booklets smuggled in mainly from Switzerland.

Initially, Jehovah's Witnesses attempted to fend off Nazi attacks by issuing a letter to the government in October 1934, explaining their religious beliefs and political neutrality. This declaration failed to convince the Nazi regime of the group's harmlessness. For defying the ban on their activities, many Witnesses were arrested and sent to prisons and concentration camps. They lost their jobs as civil servants or employees in private industry and their unemployment, social welfare, and pension benefits.

From 1935 onward, Jehovah's Witnesses faced a Nazi campaign of nearly total persecution. On April 1, 1935, the group was banned nationally by law. The same year, Germany reintroduced compulsory military service. For refusing to be drafted or perform war–related work, and for continuing to meet, Jehovah's Witnesses were arrested and incarcerated in prisons and concentration camps. In 1936 some 400 Jehovah's Witnesses were imprisoned at Sachsenhausen concentration camp.

In 1936 a special unit of the Gestapo (Secret State Police) began compiling a registry of all persons believed to be Jehovah's Witnesses, and agents infiltrated Bible study meetings. By 1939, an estimated 6,000 Witnesses (including those from incorporated Austria and Czechoslovakia) were detained in prisons or camps. Some Witnesses were tortured by police in attempts to make them sign a declaration renouncing their faith, but few capitulated.

In response to Nazi efforts to destroy them, the worldwide Jehovah's Witness organization became a center of spiritual resistance against the Nazis. An international convention of Witnesses, held in Lucerne, Switzerland, in September 1936, issued a resolution condemning the entire Nazi regime. In this text and other literature brought into Germany, writers broadly indicted the Third Reich. Articles strongly denounced the persecution of German Jews, Nazi "savagery" toward Communists, the remilitarization of Germany, the Nazification of schools and universities, Nazi propaganda, and the regime's assault on mainstream churches.

The children of Jehovah's Witnesses also suffered. In classrooms, teachers ridiculed children who refused to give the "Heil, Hitler!" salute or sing patriotic songs. Classmates shunned and beat up young Witnesses. Principals expelled them from schools. Families were broken up as authorities took children away from their parents and sent them to reform schools, orphanages, or private homes, to be brought up as Nazis.

After 1939 most active Jehovah's Witnesses were incarcerated in prisons or concentration camps. Some had fled Germany. In the camps, all prisoners wore markings of various shapes and colors so that guards and camp officers could identify them by category. Witnesses were marked by purple triangular patches. Even in the camps, they continued to meet, pray, and make converts. In Buchenwald concentration camp, they set up an underground printing press and distributed religious tracts.

Conditions in Nazi camps were generally harsh for all inmates, many of whom died from hunger, disease, exhaustion, exposure to the cold, and brutal treatment. But, as psychoanalyst Bruno Bettelheim and others have noted, Witnesses were uniquely sustained in the camps by the support they gave each other and by their belief that their suffering was part of their work for God. Individual Witnesses astounded their guards with their refusal to conform to military-type routines like roll call or to roll bandages for soldiers at the front. At the same time, Witnesses were considered unusually trustworthy because they refused to escape from camps or physically resist their guards. For this reason, Witnesses were often used as domestic servants by Nazi camp officers and guards.

According to Rudolf Höss, Commandant of Auschwitz, SS Chief Heinrich Himmler often used the "fanatical faith" of Jehovah's Witnesses as an example to his own SS troops. In his view, SS men had to have the same "unshakable faith" in the National Socialist ideal and in Adolf Hitler that the Witnesses had in Jehovah. Only when all SS men believed as fanatically in their own philosophy would Adolf Hitler's state be permanently secure.

In the Nazi years, about 10,000 Witnesses, most of them of German nationality, were imprisoned in concentration camps. After 1939, small numbers of Witnesses from Austria, Belgium, Czechoslovakia, the Netherlands, Norway, and Poland (some of them refugees from Germany) were arrested and deported to Dachau, Bergen-Belsen, Buchenwald, Sachsenhausen, Ravensbrück, Auschwitz, Mauthausen, and other concentration camps. An estimated 2,500 to 5,000 Witnesses died in the camps or prisons. More than 200 men were tried by the German War Court and executed for refusing military service.

During the liberation of the camps, Jehovah's Witnesses continued their work, moving among the survivors, making converts.