The European Red List of Trees, published by the International Union for Conservation of Nature (IUCN) says invasive species, unsustainable logging and urban development have put 58% of Europe's 454 endemic tree species at risk.
Of these, it describes 66 species (15%) as being "critically endangered", though these are chiefly of genus Sorbus, which consists of "complex arrays of hybrids" across the Continent including the UK.
The horse chestnut (Aesculus hippocastanum) has meanwhile been assessed as "vulnerable" following declines caused by the leaf-miner moth (Cameraria ohridella), which is thought to have first appeared in the tree's native region of the Balkans before spreading across Europe where the tree has been introduced.
This has added to to pressures from logging, forest fires and tourism, the report says, leaving no more than 10,000 trees scattered aross its native range.
Head of the IUCN Red List Unit Craig Hilton-Taylor said: "Measures for conserving these threatened species, and many other overlooked species highlighted in the European Red List assessments, need to be integrated into regular conservation planning and land management."
Almost half of Europe's shrub species are also threatened with extinction, the IUCN says.