There is Robin Hood's Oak in Sherwood Forest, Nottinghamshire, England, Great Britain, UK, Europe, The Earth. Legend says it was where Mr. Hood and his mates had their base, but if he didn't really exist and the tree is reckoned to be about 800 years old (and may actually be several trees that have grown together), this is somewhat unlikely.
Someone ought to mention Bartek as well. Go on - get posting!
It's interesting that more often than not in European culture, it is the oak (Quercus spp.) that carries such myths.
Judas tree
Cercis siliquastrum.
edit: Sorry I edited this about 5 times! I just like editing!