Is a foot fetish considered deviant sexual behavior?

"Deviant" is sort of a tricky Word. Most people don't have a foot fetish, so in the statistical sense, it's deviant. But as long as you're playing with a willing partner, it's not a problem.

BUT ... if you've pressured your partner into something they aren't comfortable with; if the foot is more important than the person attached to it; if the fetish is controlling you (as opposed to you controlling the fetish), you might want to talk to a mental health professional who can help you to regain control of the fetish.