Nikkō is most easily reached from Tokyo by the Tōbu Nikkō Line from Asakusa station. The Limited Express Revaty runs several times daily and takes about two hours to Tobu-Nikkō station, arriving in the town centre. The regular Express service takes slightly longer but is cheaper. The Tobu-Nikkō pass combines the train ticket with unlimited bus travel in the Nikkō area and is good value for a day trip.
JR trains run from Ueno and Shinjuku to JR Nikkō station (also in the town centre) via Utsunomiya, where a change is required. The journey takes about two hours with the connection. JR Pass holders will prefer this route.
From Utsunomiya, the Nikkō Line takes about 45 minutes. Utsunomiya is itself on the Shinkansen from Tokyo (50 minutes), making a possible combination with a gyoza lunch in Utsunomiya — the city is famous for them.