London Buses route 521 is a Transport for London contracted bus route in London, England. Running between Waterloo and London Bridge, it is operated by London General.
Route 521 commenced operating on 18 July 1992 between Waterloo Colonnade and London Bridge Station via Waterloo Bridge - Aldwych - Kingsway - Holborn - Holborn Circus - St Paus Station - New Change - Cannon Street. The route was initially operated by London General from their Waterloo (RA) garage using Leyland National 2s. The route was introduced to replace withdrawn route 513 between London Bridge to St Pauls and the withdrawn section of route 501 between Waterloo and St Pauls.
On 5 June 2002, the route was converted to low floor single deck articulated bus operation with Mercedes-Benz O530Gs.
On 2 April 2007, an Evening service was introduced.
In December 2013, brand new BYD Electrics were introduced.
In July 2015, brand new Irizar i2 EV Electrics were introduced.
On 30 April 2016, MEC50 was repainted into Red Arrow livery to celebrate 50 anniversary of the Red Arrow network.
On 27 August 2016, the route was retained by London General with brand new Enviro 200 Electric bodied BYD K9Es introduced.
In January 2017, the route was converted to full Enviro 200 Electric bodied BYD K9E operation.
- Waterloo Station Interchange
- Holborn Station
- Chancery Lane Station
- Holborn Circus
- City Thameslink Station
- St Paul's Station
- Mansion House Station
- Cannon Street Station
- Monument Station
- London Bridge Bus Station