This is the full movie from 1978. Bakshi intended to make The Lord of the Rings into two movies and this was the first part, which covers most of the events in The Fellowship of the Ring and The Two Towers. But for a variety of reasons, the second movie was never made.
It uses some fascinating experimental animation techniques and features top notch voice talent, like John Hurt as Aragorn and Anthony Daniels as Legolas.
Peter Jackson was obviously influenced by this Bakski version; the scene where the Ring Wraiths attack the hobbits in their beds in the Inn in his live action The Fellowship of the Ring is shot nearly identically to the animated film you can see here.
More info on the Bakshi Lord of the Rings