AI romantic companions — digital agents that can text, speak, flirt and are always available — are a rapidly growing social phenomenon.The number of AI companion apps rose by 700 per cent between 2022 and 2025. One of the more popular ones, Character.AI, reported about 20 million monthly active users in 2025. Their appeal is easy to understand. They are always available, highly customizable and offer a steady sense of being heard, desired and understood — at a time when loneliness and social disconnection are on the rise.Because these systems are designed to encourage attachment, people often humanize them in return. For some people, that can create the feeling of being deeply known, sometimes even more than by a human partner. Research shows that 21 per cent of romantic AI users prefer this “ultimate soulmate experience” to interacting with a real partner. The growing visibility of romantic AI companions has pushed the issue into public debate, raising a central question: If a chatbot can feel this intimate, does it count as cheating in a committed relationship? Our preliminary research suggests that, in Canada at least, people think it does. Emotional and sexual diversionInfidelity is usually understood as a violation of exclusivity, whether sexual or emotional, that diverts romantic love, attention or emotional investment away from a primary partner. Romantic AI companions are not simply entertainment or sexual tools. People often describe them as validating, emotionally responsive and easy to confide in. Some people turn to them for erotic role play or sexual exploration, while for others the bond deepens into dating or even a marriage engagement. In that sense, romantic AI companions can reproduce the very forms of emotional and sexual diversion that many already see as crossing a line. Recent research suggests this is no longer a marginal phenomenon. Surveys in the United States reveal that at least one in six adults reported interacting at least once with a romantic AI companion, and about one-third said a partner’s use would count as cheating.In another study of young adults in committed relationships, nearly two-thirds of regular users wished their partner behaved more like their AI companion. Worse than AI porn and sex toysWe surveyed 1,815 Canadian adults and asked whether they would consider a partner’s engagement with a romantic AI companion to be cheating. We also asked how they would feel emotionally and whether those views varied depending on respondents’ demographic and ideological characteristics. Our results show that about half of respondents saw a partner’s romantic companion use as infidelity, and roughly three-quarters said they would react negatively. In fact, reactions to romantic companions were about as negative as reactions to dating apps and webcamming, both of which involve a human third party. They were more negative than reactions to all other sexual technologies, such as AI pornography and sex toys. Interestingly, nearly two-thirds of AI romantic companion users kept their use from their partner.Cis women, Gen Z react negativelyThe pattern was not the same for everyone. Cisgender women were about twice as likely as cis men to say romantic companion use counted as cheating. Gen Z participants also tended to react more negatively compared to older participants. Meanwhile, individuals in non-monogamous relationships were about half as likely as participants in committed monogamous relationships to perceive romantic companion use as infidelity. Ideology matters too. In our research, higher social conservatism and religiosity were linked to stronger infidelity judgments. Participants further to the right on the political spectrum were more likely to see romantic companion use as cheating. As findings from an unpublished study, these results should be read as tentative.Exploration or betrayal?Romantic AI companions are not seen as neutral tools. They occupy a distinct relational space among sexual technologies, one that can challenge couple boundaries even in the absence of a human third party. Their significance lies not only in what they can do, but also in what they may represent within a relationship: secrecy, emotional diversion, comparison or a shift in intimacy away from a human partner. For therapists and couples alike, the key question is not simply whether romantic companion use counts as cheating, but how it develops, whether it is disclosed, what needs it serves and how partners interpret it.The distinction between privacy and secrecy is especially important here. Some may see these systems as emotional support, self-expression or private sexual exploration; others may experience them as withdrawal or betrayal. Concerns arise when romantic companion use is concealed or replaces communication or conflict resolution with a partner. Chatbots can also begin to reshape the primary relationship in ways that feel like a boundary violation.Long-term impactsIt is unclear how the use of a romantic companion unfolds within real romantic relationships over time. Research has yet to determine how romantic AI companions may influence relationship satisfaction and emotional intimacy among people in committed relationships, or the relational difficulties — such as conflict, unmet emotional or sexual needs — that may prompt them to seek these interactions. As AI-mediated intimacy becomes more visible in everyday life, answering these questions will be essential for understanding how romantic relationships are changing in an increasingly digital society.David Lafortune received funding from the Université du Québec à Montréal for this research.Valerie A. Lapointe receives funding from the Fonds de recherche du Québec - Société et Culture.Ellfie Chen does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.