The prosecution against Lord Greville Janner, a former MP and a member of the House of Lords, represents a victory for campaigners who have demanded tougher action on child abuse.
The Crown Prosecution Service (CPS) had initially declined to bring charges against the 86-year-old because he is suffering from Alzheimer's and was considered too ill to stand trial.
But after intense criticism, director of public prosecutions Alison Saunders announced he has now been charged with offences against nine victims, all but one of them aged 16 or under at the time, relating to alleged incidents between 1963 and 1988.
Prosecutors said Janner would still likely be declared unfit and any trial would therefore not result in any conviction, but said bringing charges was a chance for the alleged victims to be heard in court.
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Liz Dux, who represents many of the claimants against Janner, said they were "delighted".
"Our clients have waited long enough for their very serious allegations to be brought before a court," she said.
Police and the CPS have been under pressure in recent years to take a tougher approach to allegations of sex abuse against children, amid concerns that for generations the problem has been brushed under the carpet.
The pressure dates back to revelations that the late BBC presenter Jimmy Savile was a prolific paedophile who preyed on young people in hospitals, schools and at BBC offices for more than 50 years without being caught.
Claims against Janner have fuelled speculation about an alleged paedophile ring at Westminster, which is being examined in a wide-ranging public inquiry into child abuse set up by Prime Minister David Cameron last year.