The Reichstag fire (German: Reichstagsbrand, listen ) was an arson attack on the Reichstag building, home of the German parliament in Berlin, on Monday 27 February 1933, precisely four weeks after Nazi leader Adolf Hitler was sworn in as Chancellor of Germany. Marinus van der Lubbe, a Dutch "council communist", was the apparent culprit; however, Hitler attributed the fire to Communist agitators. He used it as a pretext to claim that Communists were plotting against the German government, and induced President Paul von Hindenburg to issue the Reichstag Fire Decree suspending civil liberties, and pursue a "ruthless confrontation" with the Communists. This made the fire pivotal in the establishment of Nazi Germany.

A German court decided later that year that Van der Lubbe had acted alone, as he himself had claimed.

The first report of the fire came shortly after 9:00 p.m., when a Berlin fire station received an alarm call. By the time police and firefighters arrived, the Chamber of Deputies (the lower house) was engulfed in flames. The police conducted a thorough search inside the building and found Van der Lubbe, who was arrested.

After the Fire Decree was issued, the Nazi-controlled police made mass arrests of Communists, including all of the Communist Reichstag delegates. This severely crippled Communist participation in the 5 March elections. After the 4 March elections, the absence of the Communists gave the Nazi Party a majority in the Reichstag, greatly assisting the Nazi seizure of total power.

As part of the effort to blame the Fire on the Communists, on 9 March the Prussian state police arrested Bulgarians Georgi Dimitrov, Vasil Tanev, and Blagoy Popov, who were known Comintern operatives. (Though the police did not know it, Dimitrov was head of all Comintern operations in Western Europe.) Ernst Torgler, head of the Communist Party, had surrendered himself to police on 28 February.

They and Van Der Lubbe were the defendants in the Leipzig Trial. All four Communists were acquitted. The responsibility for the Reichstag fire remains a topic of debate and research. The Nazis accused the Comintern of the act. However, some historians believe, based on archive evidence, that the arson had been planned and ordered by the Nazis as a false flag operation. The building remained in its damaged state until it was partially repaired from 1961 to 1964 and completely restored from 1995 to 1999. In 2008, Germany posthumously pardoned Van der Lubbe under a law introduced in 1998 to lift unjust verdicts dating from the Nazi era.