A railfan or rail buff (American English), railway enthusiast (Australian/British English), or (often with a more specialized meaning, described below) trainspotter (British English), is a person who is strongly interested, in an amateur capacity, in railroads. Railfans can be found worldwide.

Excessively enthusiastic railfans are sometimes referred to pejoratively as "foamers", especially by American railworkers, in reference to the joking notion that they foam at the mouth in their excitement over train operations. "FRN" (for "fucking rail nut")[1] is a similarly-used term in the American rail industry. In the UK, railfans are sometimes called "grizzers" or "gricers" (the latter especially by railway staff in the Midlands). In Australia, they are sometimes called "gunzels."