The actor joined author China Miéville on the BBC to promote their new novel, "The Book of Elsewhere," which follows an immortal character who is eager to die -- which explains why the morbid topic was brought up in the first place.

As Keanu put it ... at 59 years old, he's "thinking about death all the time," especially since he described himself as "young-old."

For those concerned about his fixation on death, KR defended his mindfulness about mortality as actually being a good thing.

Here's his most positive spin on his death obsession ... "Hopefully it sensitizes [us] to an appreciation of the breath we have, and the relationships that we have the potential to have."

Keanu's confessions didn't stop there, as the actor later admitted in the interview that he did not write "The Book of Elsewhere," and gave full credit to China.

However, as the new novel is based on Keanu's "BRZRKR" comic book series, CM said the A-lister deserved more credit than he's willing to take. China added, "It wouldn't exist in the form without a lot of very thoughtful and careful work with Keanu."

This might be one of Keanu's more eccentric interviews, and the headlines about him and death will certainly be jarring. Rest easy, fans ... he's totally healthy.