Heptasteornis

Heptasteornis is the name given to a dubious genus of small alvarezsaurid dinosaur from the Late Cretaceous. The type (and only known) species is Heptasteornis andrewsi, described as a presumed gigantic prehistoric owl in 1975. It was previously included in "Elopteryx nopcsai" and indeed the holotypes of both were believed to be from the same individual as they were discovered, and initially were assigned the same specimen number. This appears to be in error however (see below).
The material was discovered in Romania by Franz Nopcsa, in the late Maastrichtian Sânpetru Formation (Rognacian faunal stage, deposited c. 68 - 66 million years ago) of the Haţeg Basin in Transylvania. The scientific name means "C.W. Andrews' Transylvanian bird", after the namer of "Elopteryx", and Ancient Greek "hepta" (ἑπτά) "seven" + "asty" (άστυ) "city" + "ornis" (όρνις) "bird"; the Latin "septum urbium" or the German "Siebenbürgen" - meaning "seven cities" or "seven castles" - were common names for the Transylvanian region throughout the centuries.
The material was originally limited to a mere two broken distal tibiotarsi, BMNH A4359 and A1528. The taxonomic status and systematic placement of these bones was much disputed and they were often considered junior synonyms of "Bradycneme" or "Elopteryx". Given the fragmentary nature of the fossils, little could be resolved and "Heptasteornis" was (and still is) considered a "nomen dubium" by many.
However, more recently the bones were reassessed as an alvarezsaurid, the first to be known from Europe, and this theory, originally proposed in 1988, has since withstood further scrutiny. "Bradycneme" and "Elopteryx" on the other hand seem to be more advanced maniraptoran theropods.
Thus, of those three enigmatic Romanian theropods the one most explicitly named a "bird" in its scientific name is almost certainly the one most distantly related to birds.