Oneitis is a situation where a man will become obsessed with one woman. Often the man is delusional and believes that a certain women is his "soulmate", and that he can't live without her. The man's obsession with this one woman virtually ensures that the relationship is doomed. Symptoms can include feelings of hopelessness, heart palpitations, dry mouth, depression, anxiety and an inability to seek out other romantic or sexual relationships. Oneitis is the opposite of spinning plates.

Troy Davis says that oneitis is "the high watermark of ‘blue pill’ thinking".[1]

The Great Gatsby contains one of the most famous instances of oneitis in fiction.

A partner or ex-partner of a woman with borderline personality disorder probably experiences the most severe kind of oneitis.[2] An alpha widow can also experience something like oneitis.

Heartiste describes the difference between acute and malignant oneitis as follows:[3]

Beauty + proximity = acute oneitis

Beauty + former proximity + memories = malignant oneitis

Rollo notes, "One of two things generally happen for the Blue Pill guy who gets his wish and achieves intimacy with his ONEitis girl. He either defaults to supplication with her, or his ONEitis idealization of her is dispelled, and she and womankind are brought back down to earth to mingle with the mere mortals. It’s important to really understand what ONEitis really is; an unhealthy attachment to an idealization."

He also notes that "part of Blue Pill conditioning is promoting the idea that the women men ought to pedestalize should base that idealization on intrinsic rather than extrinsic factors. You will find that some of the most pathetic guys with ONEitis will often pine over some of the least physically attractive women. I’ve stood in wonderment over the weeping and gnashing of teeth Blue Pill guys will display over women whom they exceed in SMV by as much as 2 points. That’s the ‘real’ ONEitis; when a guy who you know could easily do leagues better than his ONEitis girlfriend in the SMP is bawling over her, head in hands, because she’s his ‘One’. Looking at this from the outside we think ‘what the fuck man?’ and try to deductively reason with him about how much better he can do, but what we don’t wrap our heads around is that this guy was conditioned since his earliest years to believe that his ‘snowflake’ is unique in her intrinsic qualities."[4]

Illimitable Men writes:[5]

Oneitis is this dreaded genetic curse men get where they think they'll never get to pass their genes to such a high quality woman ever again, its like trauma of failing to secure/maintain a high quality woman causes a man to lose his collective shit/sense of reasoning and starts pedestalising the bitch. When you fuck other women, even if they are inferior to the woman you lost, your body is like "eh, genes getting passed on, fuck it." And that is thus how the oneitis is quelled. If you get it really bad you'll need more than one woman to move on, we're talking dozens. Voice of experience here. Fucking oneitis, the bane of mankind.