Two Russian nationals have been named as suspects in the attempted murder of former Russian spy Sergei Skripal and his daughter Yulia.
There is "sufficient evidence" to charge Alexander Petrov and Ruslan Boshirov over the attack in Salisbury, Scotland Yard and the CPS say.
They are thought to have been using the names as aliases and are about 40.
Mr Skripal, 66, and his daughter Yulia, 33, were poisoned with the nerve agent Novichok in March.
The CPS is not applying to Russia for the extradition of the two men, as Russia does not have extradition agreements with the UK. A European Arrest Warrant has been obtained in case they travel to the EU, however.
In response, the Russian foreign ministry has said the names and photographs of the men "do not mean anything to Moscow".
Police are now linking the attack to a separate poisoning on 30 June, when Dawn Sturgess and Charlie Rowley fell ill at a house in Amesbury, about eight miles from Salisbury.
Ms Sturgess died in hospital on 9 July. Mr Rowley was discharged from hospital on 20 July.
Sue Hemming, CPS director of legal services, said there was enough evidence "to provide a realistic prospect of conviction" and that it was "clearly in the public interest to charge Alexander Petrov and Ruslan Boshirov".
The offences include conspiracy to murder Sergei Skripal; the attempted murder of Sergei Skripal, Yulia Skripal and Nick Bailey; the use and possession of Novichok contrary to the Chemical Weapons Act; and causing grievous bodily harm with intent to Yulia Skripal and Nick Bailey.
Det Sgt Nick Bailey also fell ill after responding to the incident in Salisbury.
Scotland Yard's Assistant Commissioner Neil Basu, the head of UK counter-terrorism policing, said on Wednesday that Det Sgt Bailey "continues to make good progress but remains off work".
What happens now?
Analysis by BBC News diplomatic correspondent Jonathan Marcus
The decision to name two Russian individuals as suspects in the Skripal case is a significant development - raising the level of evidence on which the British government's charges are based and potentially giving added weight to calls for additional international sanctions against Moscow.
The US, along with a swathe of Britain's allies, expelled a significant number of Russian diplomats (many thought to be intelligence agents) in the wake of the initial evidence that a Russian military grade nerve agent had been used in the Salisbury attack.
Since then, the US administration has brought in some additional measures mandated by Congress - and more are likely to be on the way - even though President Trump himself has not shown great enthusiasm for further pressure on Russia.
Britain will be hoping that other countries may now show more enthusiasm for stepped-up sanctions.
The Metropolitan Police said the two men had arrived at Gatwick Airport from Moscow on 2 March and stayed at the City Stay Hotel in Bow Road, east London.
From there, they travelled to Salisbury on 4 March where Mr Skripal's front door was contaminated with Novichok.
Officers believe a modified perfume bottle was used to spray the door.
There is no risk to other guests who were staying at the hotel at the time, police said, but they want to hear from anyone who was a guest there from 4 March to 4 May.
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