Assassination of the Swedish rebel (later national hero) Engelbrekt Engelbrektsson (27 April O.S.).

Engelbrekt Engelbrektsson was a Swedish nobleman, rebel leader and military leader of German ancestry. He was the leader of the Engelbrekt rebellion in 1434 against Eric of Pomerania, king of the Kalmar Union.

Old Style (O.S.) and New Style (N.S.) indicate dating systems before and after a calendar change, respectively. Usually, they refer to the change from the Julian calendar to the Gregorian calendar as enacted in various European countries between 1582 and 1923.

May 4 is the 124th day of the year in the Gregorian calendar; 241 days remain until the end of the year.