H is an S-train service in Metropolitan Copenhagen, Denmark that serves mainly the outer part of Frederikssundbanen, running partially non-stop between Ballerup and Flintholm. It is one of the six base lines of the S-train network, running every 20 minutes all days from about 5:00 until 1:00. It is the only base line in the network whose frequency is not doubled in the daytime; instead approximate 10-minute service on the outer part of the radial is provided by extending some trains on service C from Ballerup to Frederikssund.