The President of the Royal Spanish Football Federation -- who's had the job since 2018 -- just publicly announced he was resigning during an interview with Piers Morgan, who was asking if the backlash had grown too large to ignore.

Rubiales acknowledged his defiance was now starting to affect others and the organization at large, and that he was becoming a distraction ... so he's throwing in the towel.

He does maintain his innocence -- as he's done from the start -- but says trying to keep his position was turning out to be more trouble than it's worth. After a clip of the Piers sit-down was posted, he took to Twitter to confirm he'd passed the baton on to the acting Prez.

In his lengthy statement, Rubiales says he plans to defend himself/his honor in the continuing fallout. Of course, that seems to reference the criminal complaint the female soccer player herself, Jennifer Hermoso, filed with the Spanish authorities -- alleging sexual assault.

Spanish prosecutors have already said they're taking him to court to stand trial. If convicted, he faces a fine and/or up to 4 years in prison.

Rubiales apologized for the incident shortly after it happened -- saying he got swept up in the moment ... but later suggesting it was a consensual kiss, despite Hermoso saying otherwise.

He was eventually suspended, and the head coach of the team actually got fired for defending Rubiales -- in which he commended the fact Rubiales refused to quit. It's perhaps not that surprising ... the team had said they wouldn't take the field until he was gone.