Known simply as The Old Elm (Stariyat Bryast), the field elm (Ulmus minor) serves as a symbol of Sliven in eastern Bulgaria, and features on its coat of arms. It is frequently evaluated by city authorities and its base reinforced.
Scotland's entry, Niel Gow's Oak in Perthshire, came seventh, Ireland's Birr Castle Grey Poplar in Co Offaly came eighth, and Wales' Oak at the Gate of the Dead, Wrexham, was ninth.
Each of the ten had already won a national heritage tree contest.
Explaining the contest, its website said: "We are not searching for the oldest, the tallest, the biggest, the most beautiful or the rarest of trees. We are searching for the most lovable tree, a tree with a story that can bring the community together."
The award ceremony took place at the European Parliament building in Brussels on Wednesday 19 March.