Short answer: no.
I’ve heard/read this question dozens if not hundreds of times in the years I’ve been writing about sex. People are desperate to know, it seems, if masturbating while you’re in a relationship can ever be classed as cheating.
In order for me to rip this notion apart, let’s examine what “cheating” is. To many people, it is probably broadly defined as “doing sexual or romantic things with someone who isn’t your partner.” That’s sort of fine, but I don’t think it goes far enough. Lots of us do sexual and/or romantic things with people other than our primary partners all the time, but with their knowledge and consent. That’s kinda what consensual non-monogamy is! And yet it is still possible to cheat in an open or polyamorous relationship.
I propose the working definition that cheating is willfully and knowingly breaking the rules of your relationship in order to engage sexually or romatically with another person without your partner’s knowledge and/or consent.
“Yourself” does not count as “another person.”
You cannot cheat on your partner with yourself. You simply cannot. Doing anything with your own body, and only your own body, is a universe away from doing something with another person behind your partner’s back.
In my view, saying that touching your own body sexually is cheating makes about as much sense as saying that going to a coffee shop or restaurant by yourself counts as cheating.
You cannot cheat on your partner with yourself!
But it’s even more fundamental than that. Your body is yours.
You have an absolute, inalienable and irrefutable right to your own body. It belongs to you, and nobody else. Always.
Look, even if you think you’re the most absolute subby sub who ever subbed and you’ve given complete control over your body to your Dominant… you can still take that back at any time. You get to say “nope” (or “red” or “canary” or whatever means no according to your agreements) and have everything stop. Period, the end, done.
You have the right to do what you like with your own body. And that includes to engage in a sexual relationship with yourself.
You may have mutual agreements with your partner around sexual activity with others outside your relationship, and you should absolutely stick to those (or if you can’t, renegotiate the rules or end the relationship.) But your partner does not own your sexuality. They do not have a right to have any and all of your sexual activity and feelings directed at them exclusively forever more. (Nor is this realistic. Show me a sexual person in a relationship who has never had even a fleeting sexual thought about someone other than their partner, and I’ll show you a liar.)
What if my partner is masturbating all the time instead of having sex with me?
If you’re dissatisfied with the sexual relationship you have with your partner, that’s a conversation the two of you need to have.
“We’re not having as much sex as I would like, can we talk about that?” is a really valid thing to raise. Being able to talk frankly about sex is important to a strong and healthy relationship. And in a good relationship, your partner will be willing to have the conversation and work to solve the problem so that you’re both happy and satisfied. But “forbid masturbation” isn’t the answer. This is just likely to lead to resentment, hurt feelings, and sneaking around and dishonesty.
So no. Masturbation is not and cannot ever be cheating.
Anyone who tells you otherwise is full of shit. Also, trying to control what you do with your own body is a red flag for abuse.
Wank away guilt-free. And walk away from anyone who thinks that being in a relationship means they can take away your bodily autonomy.