The individuals, said to be members of the Russian Federal Security Service, will be subject to travel bans and asset freezes, the Foreign, Commonwealth and Development Office (FCDO) said.
The department believes the seven people were “directly responsible” for planning or carrying out the attack on Navalny on August 20 last year.
Foreign Secretary Dominic Raab said: “Since the horrific poisoning of Alexei Navalny took place a year ago, the UK has been at the forefront of the international response against this appalling act.
“Through our chemical weapons sanctions regime and at the Organisation for the Prohibition of Chemical Weapons, we are sending a clear message that any use of chemical weapons by the Russian state violates international law, and a transparent criminal investigation must be held. We urge Russia to declare its full stock of Novichok nerve agents.”
Mr Navalny, one of the most vocal critics of Russian president Vladimir Putin, fell ill on a flight to Moscow and was found to have been poisoned with novichok.
The nerve agent was also used in the Salisbury poisonings in 2018.
Mr Navalny, 45, has since been jailed in Russia on embezzlement charges.
The UK previously already imposed sanctions on six Russians, including the director of the Federal Security Service, who the government holds responsible for the poisoning.
The UK and United States issued a joint statement condemning the “assassination attempt” on Mr Navalny.
The statement read: “We welcome sanctions actions made by international partners and will continue to co-ordinate with international partners on further measures.
“Today, the UK and the US join in taking further action against the individuals directly responsible for carrying out the poisoning of Mr Navalny.
“As we did after Russia’s use of a chemical weapon against the Skripals in the United Kingdom in March 2018, we continue to underline that there must be accountability and no impunity for those that use chemical weapons.”