Bi-national couples who are not married often assume the route is closed to them, or vanishingly rare, when the difficult part is documentation rather than eligibility. Knowing which elements actually decide these cases separates a demanding process from an impossible one.
Yes — it's one of the more well-trodden immigration routes here, it's just paperwork-heavy. The path: pass the basisexamen inburgering buitenland (a basic A1-level Dutch and "Knowledge of Dutch Society" exam, sat at the Dutch embassy in your home country) unless you're exempt — EU/EEA, US, UK, Canadian, Australian, Japanese and a few other nationalities usually are. Then apply for the MVV (provisional residence visa) together with the residence permit in one combined procedure; IND's statutory decision period is 90 days, fee €254. What actually makes these succeed: a sponsor with steady, well-documented income at or above the reference minimum-wage level IND publishes twice a year, and solid proof the relationship is "durable and exclusive" — a registered partnership or notarial cohabitation contract helps enormously, backed by a joint address, shared finances, and a real correspondence history if you weren't already living together. Sloppy or late paperwork (the exam result is only valid a year) is what turns a straightforward case into a rejected one, not the relationship itself.