Social Democratic Union

Social Democratic Union may refer to:

• Social Democratic Union (Croatia)
• Social Democratic Union (Ireland), started by Tommy Broughan in 2014 after he left the Labour Party
• Social Democratic Union (Latvia)
• Social Democratic Union (Serbia)
• Social Democratic Union (Romania)
• Social Democratic Union (Ukraine)
• Social Democratic Union of Macedonia
• Social Democratic Union of Workers and Smallholders, a political party in Finland
• Social Democratic Union 'Proletarian', a political party in Bulgaria
• Social Democratic Unionists, a political party in Syria
• Polish Social Democratic Union, defunct political party in Poland