Members of the Rail, Maritime and Transport union (RMT), Aslef, Unite and the Transport Salaried Staffs’ Association (TSSA) will stage a co-ordinated walkout, causing huge disruption to services.
A reduced timetable has been published, showing that just 11% of rail services will run, with some areas having no trains.
It will be the first time the unions have walked out on the same day, so services will be more significantly disrupted than on previous strike days.
Trains will start later in the morning and finish earlier in the evening, and there will be no trains at all across large parts of the network.
Unlike previous strike days, this Saturday there will be no trains between London and a number of other major UK cities – including Edinburgh, Manchester, Liverpool, Birmingham, Newcastle, Brighton and Norwich.
Another strike will be held on October 8.
Delegates travelling to the Conservative Party conference this weekend will be among those affected by the disruption.
Those passengers who must travel – including those looking to participate in or watch the London Marathon – are advised to plan ahead and check when their last train will depart.
Passengers are also advised that there is likely to be some disruption in the early morning of Sunday October 2 as workers return to duties.
Andrew Haines, Network Rail chief executive, said: “Despite our best efforts to compromise and find a breakthrough in talks, rail unions remain intent on continuing and coordinating their strike action.
“This serves only to ensure our staff forgo even more of their pay unnecessarily, as well as causing even more disruption for our passengers and further damaging the railway’s recovery from the pandemic.
“Passengers who want to travel this Saturday, and indeed next Wednesday and next Saturday, are asked only to do so if absolutely necessary. Those who must travel should expect disruption and make sure they check when their last train will depart.”
Daniel Mann, director of industry operations at Rail Delivery Group, said: “These strikes are unnecessary and damaging. They disrupt passengers’ plans, undermine struggling businesses, hit major events and harm the industry’s recovery.
“It is particularly disheartening that this weekend’s strike will hit the plans of thousands of runners who have trained for months to take part in the iconic London Marathon.
“That will also punish the many charities, large and small, who depend on sponsorship money raised by such events to support the most vulnerable in our community.
“While we have done all we can to keep some services running, passengers should only travel by rail if absolutely necessary.
“Passengers with advance, off-peak or anytime tickets affected by the strikes on 1 October can use their ticket on the day before the booked date, or up to and including 4 October. Passengers can also change their tickets to travel on an alternate date or get a refund if their train is cancelled or rescheduled.”