Długosiodło [dwuɡɔˈɕɔdwɔ] is a village in Wyszków County, Masovian Voivodeship, in east-central Poland.

On August 5, 1262, Długosiodło was the site of a battle between Masovian knights and the combined forces of Lithuania under chief Treniota and Ruthenians of Halych under prince Shvarno.

[2] Following the joint German-Soviet invasion of Poland, which started World War II in September 1939, the village was occupied by Germany.

In October 1939, the entire Jewish population was ordered to leave within an hour, abandoning their homes and taking only what they could carry.

The organizations were soon unified into a district of the Home Army under the cryptonym "Opocznik" ("wheatear") by Major Eugeniusz Mieszkowski nom de guerre Ostry.