The Lord of the Rings (1978), directed by Ralph Bakshi.
This covers the story up to the battle at Helm's Deep, which is about the same as Peter Jackson's first two films. The final part was never made by Bakshi.
It has a mix of animation styles but is more sedate than his earlier work. He later said that rotoscoping live action (mostly used here and in Fire and Ice (1983)) was an interesting experiment but he wouldn't do it again. Pure animation rules!
I saw this in the theater but remembered almost nothing about it. I was skeptical when people said that Peter Jackson copied some scenes for his films, but now that seems obviously true. I would say Bakshi was his first reference with the text second.
Bakshi is more loyal to the text than Jackson, even given unavoidable condensing and simplification. We hear more of the dialogue in its proper place; Jackson tends to randomize quotes and scatter them about, sometimes in different mouths and with altered meaning. Bakshi doesn't require a moping Aragorn.
On the down side it is a curiously slack narrative without much dramatic force to move it forward. The "flight to the ford" is more of an amble. The score is generically dull (and the director hated it). Other issues:
Boromir has cow horns on his helmet.
Legolas displaces Glorfindel, just as Arwen does in the later film. Arwen is missing here, which makes sense given her character is so under-written in the books.
Frodo's escape at the Ford is strangely staged and much more protracted than it needs to be.
Treebeard (one scene only) looks like he was drawn by Dr Seuss.
Sauruman is sometimes called "Aruman", obviously a script editing error that no one caught. Makes you wonder if anyone was paying attention.
Available on Blu-ray. Wizards (1977) has better blacks; they're more of a noisy gray here. I don't know what happened: in the Wizards (1977) commentary Bakshi said that deep black is essential in adult animation; it wasn't even available when he started drawing for the movies.