This a well battered white wool felt fedora.
The rolled-up brim makes it seem much shorter, so you could call a Trilby however that would be a mistake, Trilby are a subset of Fedoras and a should be a classy quality hat with a distinct look.
Maybe this once was a classy hat, maybe it is more Homburg.
But to battered to be a Homburg, also the crown does not seem tall enough.
I can't remember where this hat came from, but its been hanging around being crushed at the bottom a box and needs a use.