Gatwick is a good deal further from central London than its name suggests, so a stay near the airport can save you a long morning.
By train
The railway station is in the South Terminal. Gatwick Express, Thameslink and Southern trains leave from it. The Gatwick Express takes about 30 minutes to London Victoria, per the earlier draft of our airport page and secondary sources. We have not checked fares or timetables.
From the North Terminal
Take the free shuttle train to the South Terminal and follow the signs for the station. See getting between terminals.
If you are staying near the airport
A hotel at the terminal puts you a short walk from the station if you stay at the South Terminal, and a short train ride away if you stay at the North.
What we have not checked
Fares, the last trains at night and the first trains in the morning. Check them before relying on a train for an early or late flight.