Croatian Democratic Alliance of Slavonia and Baranja (Croatian: Hrvatski demokratski savez Slavonije i Baranje, HDSSB) is a regionalist and right wing populist political party in the Eastern Croatian region of Slavonia.
It was formally founded on 6 May 2006, but had its origins one year earlier, when the group of local Croatian Democratic Union politicians, led by War of Independence veteran Branimir Glavaš, launched a political organisation with a very similar name, the Croatian Democratic Assembly of Slavonia and Baranja (Croatian: Hrvatski demokratski sabor Slavonije i Baranje) at the eve of May 2005 local elections. The stated aim of new group was the regional reorganisation of Croatia in order to improve conditions in Slavonia, which was - according to Glavaš and his supporters - neglected by central government in Zagreb.
The HDZ leadership under Ivo Sanader denounced that platform and ejected Glavaš out of the party. However, most of the local HDZ organisation followed Glavaš and his independent election ticket that won a relative majority in the Osijek-Baranja County and City of Osijek assemblies. That group of independents became the HDSSB on 6 May 2006. In the Croatian parliamentary election, 2007 they received 44,552 votes or 1.8% of the electorate, and won 3 seats in the Croatian Parliament. They improved their position in Croatian Parliament in next election by winning 6 seats.
In 2014, HDSSB became part of the Alliance for Croatia coalition, which was dissolved in 2015.