High Quality Content by WIKIPEDIA articles! Socialist Youth International (in German: Sozialistische Jugend-Internationale, French: L`Internationale de la Jeunesse Socialiste) was an international union of socialist youth organisations. It was founded in Hamburg 1923, through the merger of the Young Workers` International and the International Community of Socialist Youth Organisations. The formation of SYI was parallel to what of the Labour and Socialist International, and LSI and SYI were closely connected.