The London–Aylesbury line is a railway line between London Marylebone and Aylesbury, going via the Chiltern Hills; passenger trains are operated by Chiltern Railways. Nearly half of the line is owned by London Underground, approximately 16 miles (26 km) – the total length of the passenger line is about 39 miles (63 km) with a freight continuation. The line is part of the former trunk route, the Great Central Main Line.