Mäntsälä rebellion (Finnish: Mäntsälän kapina) was the failed coup attempt by the Lapua Movement to ovethrow the Finnish government.

On February 27, 1932 some 400 armed members of the Suojeluskunta militia interrupted a meeting of Social Democrats in Mäntsälä with small arms fire. In the next few days, leading members of the Lapua Movement (Lapuanliike) and hundreds of armed members of Suojeluskunta arrived at Mäntsälä. The former Chief of Staff of Finland's Army, Lieutenant General Wallenius also joined the leadership of the rebellion. The men refused to disperse and demanded the cabinet's resignation and a change in political course.

Two days later the cabinet ordered the leaders of the Lapua movement arrested using the Protection of the Republic Act which the movement itself had urged for a year before. Army units began preparing as the commander of the army, Lieutenant General Aarne Sihvo was prepared to use force to end the rebellion. Orders were given to reinforce the defence of Helsinki with tanks and artillery in case the situations would escalate. As the tensions grew, so did the consumption of alcohol among the instigators.

On March 2 president Svinhufvud gave a radio speech, where he urged the militiamen to return home and promised that only the leaders would be punished. The men dispersed and the leaders were arrested a few days later. During the spring the Lapua movement was disbanded.

The Mäntsälä rebellion can be considered the peak of the conflict between rightist and leftist factions, whose relations had been tense after the Civil War. In the coming years the economic situation in Finland would improve and the radical movements would lose support.