The Unionist Democratic Union (Arabic: الاتحاد الديمقراطي الوحدوي; French: Union démocratique unioniste) is a political party in Tunisia with pan-Arabist ideology.

[3] Its founder and first secretary-general Abderrahmane Tlili had been a member of the RCD before he founded the UDU in order to gather Arab nationalists, including Baathists and Nasserists, in a party that was close to the government.

[4] The party publishes a newspaper, entitled Al Watan.

[3] In 1994, the electoral law was changed, ensuring the parliamentary representation of minor parties.

In the election for the Constituent Assembly after the Tunisian revolution of 2011, the UDU failed to win any seats.