What is personified in this poem O wild West Wind thou breath of Autumns being from whose unseen presence the leaves dead are driven like ghosts an enchanter fleeing?

The personification in the poem is the West Wind. The poem refers to the West Wind as "thou breath of Autumn's being," giving it a human-like quality. The West Wind is also described as "an enchanter," which is a personification of its power to transform the landscape and drive the dead leaves like ghosts.