One penis policy

What is one penis policy?

One penis policy (abbreviated OPP) is an arrangement within a non-monogamous relationship where the man may have several female partners, but his female partner only other women. The rule allows exactly one penis in the relationship: his own. In poly circles the OPP counts as one-sided and is widely criticized.

What a one penis policy looks like in practice

The OPP almost always arises in a couple of a man and a woman who open the relationship. He dates other women without it causing tension. The moment she wants to date a man, it becomes a problem, and so a rule appears: she may see women, no men. Elisabeth Sheff, sociologist and author of the major American study on polyamory, describes that this rule can be explicit, a clear “no other men”, or implicit, where it only blows up when she dates a man and makes no difference when she is with a woman. In both forms it comes down to the same thing: her choice is bounded by his discomfort, not by an agreement that applies to both.

Where the OPP comes from

The rule grows out of an old double standard around sex. Sheff points to the mainstream male socialization that demands exclusive sexual access to “his” woman, and to the double standard that admires a man with many partners and disapproves of a woman with as many. Because of that, some heterosexual men can manage to date several women themselves, but not to share their partner with another man. Equality between the sexes, according to Sheff, is exactly what sets polyamory apart from older, male-centered forms of non-monogamy. As she puts it: “Gender parity is key in polyamory and one of the primary distinguishing features that differentiates polyamory from more traditional or androcentric forms of consensual non-monogamy like polygyny.” In practice an OPP turns polyamory into an extended form of polygyny, in which one man has several women.

Why couples still choose it

The appeal sits almost entirely on his side. He keeps the certainty that no other man comes into view, while his own room widens, and that feels like a way to manage jealousy and insecurity without throwing the relationship fully open. Sometimes it is presented as something she wants too, because she is only attracted to women. So what it delivers is mainly calm for him. For her it rarely delivers anything, and that is where the arrangement honestly chafes. The Gender & Sexuality Therapy Center points out that an OPP often reduces her bisexuality to something for his pleasure, and that the rule assumes attraction to a man is a bigger threat than attraction to a woman. It does not solve jealousy: it only moves it to one permitted direction.

How people fill in the rule

Roughly two forms occur. The first is the outspoken agreement, in which the couple names the OPP literally and sets it as a condition before the relationship opens. The second is the silent version, which is never agreed out loud but is enforced through anger, withdrawal, or a scene the moment she names a man. Sheff describes exactly that difference. In both cases the power to set the limit sits with the partner who has the penis, and that is what makes the term so sharp.

What an OPP is not

“An OPP is just a personal boundary.” A boundary is about your own behavior, for instance what you will or will not do. An OPP prescribes what the other may do, and that is a rule, not a boundary.

“It is about safety and STIs.” Then the rule would apply to every partner and every risk. An OPP looks at sex, not at whether people practice safer sex, and so it falls outside that explanation.

“An OPP is the same as an open relationship.” In an equal open relationship the same agreements apply to both. With an OPP they do not, and that difference is exactly what the criticism rests on.

What I see myself

Women who write to me from an open relationship sometimes tell me this rule literally, without knowing its name. He may, she may “as long as it is not a man”. What strikes me in that is how often the arrangement is explained as something practical, while on balance one person is the one giving up. I’m not a relationship therapist and your agreements are not mine to decide. But I do notice that the conversation only gets honest once both name what the rule actually protects, and whose.

More reading on the one penis policy

Within this glossary, ethical non-monogamy explains what the OPP relates to, and polyamory why equality is the starting point there.

Beyond this site, Elisabeth Sheff wrote about the OPP from her years of research into poly families.

Where this fits on this site

I’m not a matchmaker and not a relationship therapist. What I do is meet a woman who is herself seeking the room that lies lopsided at home, and that is about her, not about a rule someone else sets. If you want to know how such a date with me goes, look at my services.

Sources

• Addressing Bias Against SOPO VEE OPP Polyamory. Nafees Alam, Journal of Popular Romance Studies, 15.1, 2026. Gives the definition “The one penis policy (OPP) refers to a consensual arrangement where a cisgender woman agrees to have no more than one cisgender male partner”.
• The One Penis Policy. Elisabeth A. Sheff, PhD, Psychology Today, 2016. Gives the distinction between the explicit and the implicit rule, the double standard and male socialization behind it, and the observation that equality between the sexes sets polyamory apart from polygyny.

Related terms

The one penis policy is a contested form of ethical non-monogamy. The terms below place it in that broader field.

• Ethical non-monogamy. The overarching practice of several relationships with everyone’s consent, of which the OPP is a disputed variant.
• Polyamory. The form that takes equality between partners as its starting point, exactly what an OPP lacks.
• Open relationship. The equal alternative, in which the same agreements apply to both.
• DADT. Another arrangement that places limits on what you know of each other’s contacts, don’t ask don’t tell.
• Metamour. Your partner’s partner, the person an OPP wants to keep out precisely when it is a man.