The Croxley Rail Link is a railway engineering project in the Watford and Three Rivers districts of Hertfordshire, England. When complete, Watford branch services on the London Underground's Metropolitan line will be diverted at Croxley Green from the current terminus at Watford tube station onto the alignment of the disused Watford and Rickmansworth Railway between Croxley Green and Watford High Street stations before continuing to Watford Junction.