The Widened Lines (also known as the City Widened Lines; formerly known as the Moorgate Line) is a double-track railway line forming part of the Thameslink route between St Pancras and Farringdon within Central London.

For most of their life the Widened Lines ran from King's Cross to Moorgate, and were completed in 1866 when the Metropolitan Railway was widened from two to four tracks between King's Cross and Farringdon (hence the widened name) and a four-track railway opened from there to Moorgate.

The tracks were owned by the Metropolitan Railway but were used mainly by other railway companies. Connections to the Great Northern Railway (GNR) at King's Cross and London, Chatham and Dover Railway (LC&DR) at Farringdon allowed cross-London services to run. There was very soon a connection to the Midland Railway at St Pancras, near King's Cross. In the early 20th century competition led to the cross-London services being withdrawn, although the GNR and Midland services into Moorgate survived. The former GNR services were diverted via the Northern City Line to Moorgate in 1976, and in 1988 the cross-London route reopened for Thameslink. The line east of Farringdon closed in 2009 to allow the platforms at Farringdon to be extended to take 12-car trains.