A £20m scheme will see 17 bridges permanently lit along the River Thames, the Mayor of London has said.
Sadiq Khan is appealing for teams to design a light installation to illuminate crossings from Albert Bridge in Chelsea to Tower Bridge in the City.
It is claimed the project will be the world's longest "free outdoor river gallery".
Funding will be raised largely from private sources, the newly-formed Illuminated River Foundation has said.
Mr Khan, who has confirmed a grant £250,000 towards the competition, says the scheme will encourage investment and increase use of the river and bridges.
A £250,000 grant from the Rothschild Foundation will also help to fund the contest, while The City of London has also pledged £500,000 towards the later stages of the project.
"This is a really exciting opportunity to breathe new life through the heart of London each night," Mr Khan said.
The scheme is expected to cost in the region of £20m, according to the Illuminated River Foundation, which claims most of the funding will come from the private sector.
From west to east, the 17 bridges and the years they opened are:
- Albert Bridge, 1873
- Chelsea Bridge, 1937
- Grosvenor Bridge, 1859
- Nine Elms Bridge (in development)
- Vauxhall Bridge, 1906
- Lambeth Bridge, 1932
- Westminster Bridge, 1862
- Hungerford Bridge, 1864 and Jubilee Bridge, 2002
- Waterloo Bridge, 1945
- The Garden Bridge (in development)
- Blackfriars Bridge, 1869
- Blackfriars Railway Bridge, 1886
- Millennium Bridge, 2002
- Southwark Bridge, 1921
- Cannon Street Railway Bridge, 1866/1982
- London Bridge, 1973
- Tower Bridge, 1894
The count of bridges includes two which are not yet completed - the Nine Elms and Garden bridges.
The Illuminated River International Design Competition will ask competitors to create "forward-thinking and environmentally friendly designs".
Mark Boleat, Policy Chairman at the City of London Corporation, said: "We want the City of London to be at the heart of what looks likely to be the largest art project of its kind in the world."
The shortlisted schemes will go on show in a public exhibition at the end of the year, after which a winner will be announced.