'Night Tube' weekend service to launch in September 2015
The Tube is to run a 24-hour service at weekends from 12 September 2015, it has been announced.
Passengers will be able to take the so-called "Night Tube" on Fridays and Saturdays.
Transport for London (TfL) said the service would cut journey times by an average of 20 minutes.
The RMT union said the plans had "not been properly thought through and are a disaster waiting to happen".
There will be six trains per hour through central London on the Jubilee, Victoria and most of the Piccadilly, Central and Northern lines, TfL said.
On the Northern Line, there will be eight trains per hour to meet demand at busy stations between Leicester Square and Camden Town, it added.
The service will be launched in time for England staging the Rugby World Cup, which will be hosted in 13 venues around the country, including three in London - Twickenham Stadium, Olympic Stadium and Wembley Stadium.
Analysis - Tom Edwards, BBC London transport correspondent
Today we learnt the start date and not much more that wasn't already known about the 24-hour weekend tube.
There's no doubt it's a popular policy with Londoners.
But what is surprising is the unions have been left out of the loop - they found out the date via the media.
It's probably indicative of the poor state of industrial relations.
The 24-hour plan was initially linked to another project to cut 950 jobs and close all ticket offices.
That dispute is still rumbling on. RMT Union members are now taking industrial action - short of a strike - by not doing overtime.
What's also of note is that the current pay deal for staff comes to end in April.
This 24-hour Tube plan will no doubt affect those negotiations.
With this date now set, the pay deal could be another flashpoint in a period of relatively rapid change on the Tube.
London Mayor Boris Johnson said: "London is a bustling, 24-hour global city and by this time next year we'll have a 24-hour Tube service to match.
"As well as creating vital new jobs and giving a huge boost to our economy, the Night Tube will help millions of people to get around our city more easily and quickly."
Mike Brown, managing director of London Underground, said: "The new service will boost jobs and will benefit the economy by hundreds of millions of pounds."
RMT general secretary Mick Cash said: "This proposal is now being bulldozed through without any proper risk assessment or agreement on core issues.
"To make this plan work we need more tube staff not less if we are not going to be risking disaster at three o'clock in the morning when the West End is flooded with thousands of people fresh out of the pubs and clubs.
"As it stands at the moment the night tube plans are not properly thought through and are a disaster waiting to happen."