Yes, essentially all produced art is copyrighted simply by being created.
Is it fair use? IANAL (I am not a lawyer) but in the US "fair use" covers typically low fidelity reproduction for the purposes of parody, criticism, news or education.
However, on one hand publishers want trailers to be distributed as widely as possible because people being interested in the movie makes them money, especially if you direct traffic to a legal purchase method.
On the other hand, Disney is known for being very protective of its IP and may decide to send you a cease and desist, which you would be wise to comply with. If you make significant income from your use of their property you may also find yourself sued for royalties.
Bruce Calvert found the definitive answer:
The defence of 'fair use', where reporters or teachers use copyrighted material for socially valuable purposes, does not apply to movie trailers.
Take note in your risk calculations that is was in fact Disney that was the winning party in that case.