Bolesław I's intervention in the Kievan succession crisis

Bolesław I's expedition to Kiev
	Part of the Kievan succession crisis of 1015–1019
	; Kievan Rus' in the 11th century, with adjoining regions
Date	June–September 1018
Location	Kievan Rus'
Result	Bolesław and Sviatopolk victory Bolesław defeats Yaroslav and sacks Kiev; Cherven Towns are annexed into Poland; Sviatopolk becomes Grand Prince of Kiev, but is later dethroned by Yaroslav;
Belligerents
Sviatopolk loyalists; Duchy of Poland; Kingdom of Hungary	Yaroslav loyalists
Commanders and leaders
Bolesław I the Brave; Sviatopolk I	Yaroslav I
Strength
Uncertain: Germans (~300 knights), Hungarians (~500) and Pechenegs (~1,000 fighters), 2,000–5,000 Polish soldiers (est.)	Unknown but estimated as similar to opposing size

The 1018 intervention in the Kievan succession crisis by the Polish ruler Bolesław I the Brave was an episode in the Kievan succession crisis of 1015–1019, the struggle between Sviatopolk and his brother Yaroslav for the grand princely title of Kiev. It occurred when Sviatopolk's father-in-law Bolesław, ruler of Poland, intervened on Sviatopolk's behalf.

The intervention was initially successful as Bolesław defeated Yaroslav's armies, and temporarily secured the throne for Sviatopolk. But when Bolesław withdrew himself and his army from Kiev, Sviatopolk was unable to retain his position, being defeated by Yaroslav in the following year. Chronicles of the expedition include legendary accounts as well as factual history and have been subject to varied interpretations.