Smiltsena (Bulgarian: Смилцена) was the niece of Byzantine Emperor Michael VIII Palaiologos, and empress-consort (tsaritsa) of Tsar Smilets of Bulgaria.
Smilets ascended the throne of Bulgaria in 1292 and the new tsaritsa moved from her husband's provincial residence into the royal palace in Tarnovo.
To meet this threat and the invasion of the Mongol prince Chaka, Smiltsena sought an alliance with Aldimir (Eltimir), the brother of the former ruler George Terter I, who had been deposed by her husband.
Aldimir was accordingly married to Smiltsena's daughter Marina and, if this had not happened earlier, the widowed empress granted him the title of despotēs and invested him with a large dominion around Kran.
In 1299 Smiltsena attempted unsuccessfully to make an alliance with Serbian King Stefan Milutin to the exclusion of the latter's projected alignment with the Byzantine Emperor Andronikos II Palaiologos.