Florence Amerigo Vespucci Airport: Take tram T2 to Alamanni–Stazione Santa Maria Novella: about 20 minutes, frequent, and roughly €2 for a standard urban ticket (fares change—check the machine/app). It is the sensible default; skip a pre-booked transfer. A taxi is only worth it with heavy luggage or a group: the centre has a regulated flat fare, roughly €25 plus luggage supplements.
Firenze Santa Maria Novella railway station (SMN): This is the station you want: it sits on the north edge of the historic centre, a short walk from the Duomo, San Lorenzo and most central hotels. High-speed trains connect Rome in about 1½ hours, Milan in about 1 hour 40 minutes, Venice in about 2 hours and Naples in roughly 2 hours 50 minutes. Do not book Campo di Marte, Statuto or Rifredi unless your lodging is specifically nearby; regional links to SMN are frequent, but they add an unnecessary transfer.
Bologna Guglielmo Marconi Airport: Often the better flight choice than Florence, especially for Europe-wide low-cost schedules. Take the Marconi Express to Bologna Centrale (about 7 minutes; roughly €13), then a Frecciarossa/Italo high-speed train to Firenze SMN (about 37–40 minutes; fares vary, often €20–35 booked ahead). Allow 1½–2 hours airport-to-SMN in a normal connection, longer if flights are late. Avoid tight late-evening itineraries: the last useful connection is not a gamble worth taking.
Pisa International Airport: Use the PisaMover to Pisa Centrale (about 5 minutes; roughly €6–7), then a direct regional train to Firenze SMN (about 1 hour 10 minutes; roughly €9–10). Budget about 1½–2 hours door to door. It works, but Bologna is generally the stronger alternative-airport option unless Pisa’s flight price or schedule is substantially better.
Rome Fiumicino Airport: For long-haul arrivals, Rome is often more practical than Milan: take a train connection via Roma Termini, then a Frecciarossa or Italo to Firenze SMN. Plan roughly 2½–3 hours from airport to Florence and around €35–60 depending on how early the long-distance leg is booked. Do not plan this around the final train of the night.